Hallux Rigidus: Demographics, Etiology, and Radiographic Assessment

Transcription

1 FOOT &ANKLE INTERNATIONAL Copyright 2003 by the American Orthopaedic Foot & Ankle Society, Inc. Hallux Rigidus: Demographics, Etiology, and Radiographic Assessment Michael J. Coughlin, M.D.; Paul S. Shurnas, M.D. Boise, ID; Mountain Home, AR ABSTRACT Purpose: The purpose of the study was to evaluate the demographics, etiology, and radiographic findings associated with hallux rigidus in patients treated surgically over a 19-year period in a single surgeon s practice. Methods: Patients treated for hallux rigidus by cheilectomy and metatarsophalangeal joint fusion were identified from 1981 to Patients who had diabetes, inflammatory arthritis, infectious arthritis, crystalline arthritis, multiple forefoot deformities, neuromuscular disorders, or had died were excluded. A chart review and evaluation of preoperative radiographs were completed on all eligible patients. All identified patients were invited for a follow-up examination that included standard and stress radiographs, range-of-motion testing, Harris mat study, gait analysis, first ray mobility measurement, and standardized questionnaire assessment. Results: One hundred ten of 114 (96.5%) patients with a diagnosis of hallux rigidus returned for the final evaluation. Eighty cheilectomy patients (93 feet) and 30 arthrodesis patients (34 feet) were evaluated. The mean age at onset in the current study was 43 years (13 70 years) and only six patients developed symptoms at an age of less than 20 years. Hallux rigidus was graded based on a five-grade clinical-radiographic system. The mean follow-up was 8.9 years. Ninety-five percent of patients with a positive family history had bilateral disease at the final follow-up. At the initial examination in the current study, 81% of patients had radiographic and clinical evidence of unilateral disease, but at the final follow-up 79% of patients had radiographic and clinical evidence of bilateral disease. Eleven percent of patients in the present series had pes planus based on either a positive Harris mat study and/or heel valgus. There was no evidence of an Achilles or gastrocnemius tendon contracture. Radiographic analysis found that the concurrent presentation of hallux valgus and hallux rigidus was not common. Ninety-three of 127 feet (73%) had Corresponding Author: Michael J. Coughlin, M.D N. Curtis Rd., Suite 503 Boise, ID FOOTMD@aol.com For information on prices and availability of reprints call X226. a chevron or flat metatarsophalangeal joint. Thirty-five feet were noted to have mild or moderate metatarsus adductus. A long first metatarsal was no more common in patients with hallux rigidus than in the general population. The mean first ray elevatus was 5.5 mm and was well within acceptable limits of normal. The mean first ray mobility was 5 mm in arthrodesis patients and 5.8 mm in cheilectomy patients. Conclusion: Hallux rigidus was not associated with elevatus, first ray hypermobility, a long first metatarsal, Achilles or gastrocnemius tendon tightness, abnormal foot posture, symptomatic hallux valgus, adolescent onset, shoewear, or occupation. Hallux rigidus was associated with hallux valgus interphalangeus, bilateral involvement in those with a familial history, unilateral involvement in those with a history of trauma, and female gender. Metatarsus adductus was more common in patients with hallux rigidus than in the general population but a clear correlation was not found. Additionally, a flat or chevron-shaped metatarsophalangeal joint was more common in hallux rigidus patients. Key Words: Hallux Rigidus; Cheilectomy; MTP Arthrodesis INTRODUCTION Hallux rigidus is a common pathologic problem affecting the great toe, second only in incidence to hallux valgus. 12,24,52 Symptoms commonly associated with degenerative arthritis of the first metatarsophalangeal (MTP) joint were initially reported by Davies-Colley 20 in 1887, although Cotterill 11 is credited with proposing the term hallux rigidus. Preoperative symptoms and objective information from physical and radiographic examination are well documented in the literature (Table 1). Generally, this is where any agreement in the literature on hallux rigidus ends. There is conflicting demographic information on patients with a diagnosis of hallux rigidus. Furthermore, there is widespread disagreement on many clinical and radiographic parameters (Table 2). There are conflicting notions about the etiology of hallux rigidus as well. A traumatic origin is proposed 731

2 732 COUGHLIN AND SHURNAS Foot & Ankle International/Vol. 24, No. 10/October 2003 Table 1: Documented findings Symptoms Physical Examination Radiographic Findings Pain with joint motion 25,48,62 Increased size of joint 30,49 Osteophyte formation 53,61 Soft-tissue swelling 47,49 Everted gait 25,53 Loose bodies 10,61 Intolerance of shoewear 6,12 Restricted joint motion 2,54,64 Subchondral sclerosis 33,49 Widening/flattening of metatarsal head 1,44 Joint space narrowing 34,66 Table 2: Disputed findings Demographic Data Physical Examination Radiographic Findings Age of onset Arch Metatarsal articular shape Adult 28,67 Pes planus 22,68 Associated with hallux rigidus 24,49 Adolescent 2,50,54 Normal 41 Not associated 61 Presentation First ray hypermobility Hallux valgus deformity Unilateral 3,5,49 Hypermobile 2,41 Associated with hallus rigidus 46,61 Bilateral 33,62 Rigid 10,68 Not associated 29,30 Gender predilection First metatarsal length Male 33,39 Long 54,63 Female 44,49 Short 8,44 Equal or no association 5,49 by several authors, 5,33,49 while Jack 41 proposed a spontaneous onset. Still, additional authors blame poor shoewear, 2,20,24 a tight Achilles tendon, 2 or an elevated first ray. The concept of an elevated first ray or metatarsus primus elevatus (MPE) was introduced by Lambrinudi 45 in 1938 and several authors 3,6,7,9,10,22,29,41,46,56,57 have endorsed this notion while others have disputed the concept. 5,40,49 Based on the theory of metatarsus primus elevatus, several authors have recommended osteotomies to plantarflex the first ray, decompress the first MTP joint, or realign the distal metatarsal articular surface. 19,26,46,58,68,71 More recently, complications associated with these metatarsal osteotomies as a treatment for hallux rigidus have been reported. 59 The purpose of the present study was to define the demographics, associated etiologic and clinical factors, and radiographic findings in patients with isolated hallux rigidus from a single surgeon s practice during a 19-year period. A separate report documents the results of the surgical treatment of this cohort of patients. 16 MATERIALS AND METHODS One hundred forty consecutive patients underwent either a cheilectomy or first MTP joint arthrodesis as the surgical treatment for a symptomatic hallux rigidus deformity by the senior author (MJC) during the period of November 1981 to November Twenty-one patients were excluded because of a diagnosis of gout, rheumatoid arthritis, systemic lupus erythematosis, poliomyelitis, or previous pyarthrosis, and five other patients died during the study period, leaving 114 patients with a diagnosis of idiopathic hallux rigidus available for the study. Of these, four patients were unavailable; 110 (96%) returned for a final followup evaluation. Of the 114 patients, 17 had bilateral procedures. At the time of the initial examination, a total of 22 patients were diagnosed as having bilateral hallux rigidus and the remaining 92 patients (81%) were thought to have unilateral disease. Ninety-three cheilectomies and 34 first MTP joint arthrodeses were performed on the 110 patients who were evaluated at the final follow-up. Sixty-nine patients (63%) were females and the average age at surgery was 49.7 years. Preoperative Findings Preoperatively, 21 patients had moderate pain and the remainder had severe or quite severe pain. While all patients complained of pain in the first MTP joint, the primary complaint of one half of the patients (55/110 patients) was the first MTP joint dorsal bony prominence while for the other half (55/110 patients) the

3 Foot & Ankle International/Vol. 24, No. 10/October 2003 HALLUX RIGIDUS 733 Table 3: Preoperative complaints of patients with hallux rigidus Stiffness Pain Locking Cosmesis Supinated Able to Rise Painful MTP Foot with Gait up on Toes Dorsal Joint Bump Pain Number of patients Total number of patients = 110. major complaint was arthralgia. Other major complaints included joint stiffness, an everted gait, and joint locking (Table 3). Preoperative range of motion was recorded from the chart review. Range of motion was measured with a goniometer using the midaxial line of the proximal phalanx and the plantar surface of the foot as reference points. Pathologic specimens were routinely sent for histologic evaluation prior to 1988 and these reports as well as any sent subsequently were evaluated to determine the histologic diagnosis. Follow-up Evaluation The mean duration of follow-up was 8.9 years (range, years). At the time of the final follow-up, patients were assessed with a standardized questionnaire and examination. Patients were questioned about their history including the following: family history of great toe problems, age of onset, duration of pain or symptoms, prior fracture of the toe or specific injury, job effect, and shoewear effect on their great toe. The physical examination included inspection and palpation of the foot with attention to posture, great toe and ankle range of motion, gait pattern, first ray mobility, and appearance. Both feet were examined on all patients. The patients were examined in a seated and supine position (knee flexed and extended) with attention to the Achilles tendon tightness. Care was taken to maintain the hindfoot in a neutral position, with the talonavicular joint reduced to eliminate transverse tarsal or subtalar motion, 4,21,55 during the Achilles or gastrocsoleus assessment. The patient s stance and gait were assessed with attention to alignment of the hindfoot and foot position with ambulation. Hindfoot valgus was assessed by manual inspection of the posterior heel in the standing patient. An angulation in excess of 6 of valgus was arbitrarily considered to be abnormal. Passive MTP and ankle joint motion was measured with a goniometer and recorded; the plantar aspect of the foot was considered neutral. Harris mat studies were performed on all patients to assess arch height. Patients were asked to stand 18 inches from the Harris mat and then step forward placing the foot onto the center of the prepared mat and then continue to walk forward beyond the mat leaving an imprint of their arch height 14,36 (Fig.1,AandB). First ray mobility was measured on all patients utilizing the device and method reported by Klaue et al 43 (Fig. 2). First ray mobility was measured on all feet. This noninvasive device for measuring first ray mobility was utilized by placing the forefoot into the device in a plantigrade position; the first ray was left free so that the micrometer at the first metatarsal head could measure dorsal-plantar or sagittal plane mobility. Manual force was applied in a dorsal/plantar direction until a clear stop or endpoint to motion was noted in each direction. The maneuver was repeated 10 times for each ray and Fig. 1: A Harris mat study was utilized to measure arch height: A, Harris mat study demonstrates a normal arch with a value of ( 1); B, demonstrates a low arch with a value of (+4). See Appendix A for information on measurement technique.

4 734 COUGHLIN AND SHURNAS Foot & Ankle International/Vol. 24, No. 10/October 2003 Fig. 2: Measurement of first ray mobility by Klaue s device. 43 See Appendix B for information on measurement technique. the mean was recorded as the value. Normal first rays have up to 9 mm of mobility or dorsal excursion. 43 A classification scheme for hallux rigidus was used to grade the severity of the degenerative joint changes preoperatively. 16 With Grade 0 there was a normal radiograph, no pain, and only stiffness or slight loss of MTP joint motion; with Grade 1 there was intermittent joint pain, mild restriction of MTP joint motion, and minor narrowing of the MTP joint space; with Grade 2 there was more constant joint pain, moderate restriction of MTP joint motion, and moderate joint space narrowing with osteophyte formation; with Grade 3 there was constant joint pain; however, there was not pain at the midrange of MTP joint motion, 25 moderately severe restriction of MTP joint motion (<20 total motion), extensive osteophyte formation and severe joint space narrowing; with Grade 4 the radiographic findings were identical, but on clinical examination, patients exhibited midrange pain on passive manipulation of the MTP joint. Radiographic Evaluation Standardized preoperative weightbearing radiographs 15 were reviewed. The shape of the distal first metatarsal articular surface was noted and recorded as oval, flat, or chevron 12 (Fig. 3, A C) and the articular width of the MTP joint was determined by a summation method using six separate measurements (Fig. 4). Elevation of the first ray (MPE) was measured as described by Horton et al. 40 On the weightbearing lateral radiograph, the difference between the dorsal cortices of the first and second metatarsals measured at the head neck junction was recorded in millimeters. A normal value is 8 mm or less. 40 A second measurement was used to evaluate the position of the first metatarsal relative to the plantar aspect of the foot called the first metatarsal declination angle (1-MDA). The first metatarsal declination angle was measured as described by Bryant et al. 5 and normal values are reported to range from 19 to 25 5 (Fig. 5). First metatarsal length was measured in comparison to the second metatarsal length (metatarsal protrusion distance) on the preoperative AP radiograph 36 (Fig. 6). Values were measured and recorded in millimeters; measurements within the range of +1 to 1mmwere considered to be equal length. Sesamoids were subjectively evaluated based on their appearance on the radiographs and graded as irregular in shape, cystic, or normal. Loose bodies were noted if present on preoperative and/or postoperative radiographs and the radiodensity (sclerosis) about the MTP joint was graded as well. Sclerosis was recorded as 0 (no sclerosis), +1 (mild), +2 (moderate), or +3 (severe) on the preoperative radiographs. Angular measurements were made according to the guidelines as set forth by the American Orthopaedic Foot and Ankle Society (AOFAS) Committee on Angular Measurements 15 (Fig. 7). The hallux valgus angle (normal 15 or less), the 1 2 intermetatarsal angle (normal 9 or less), and the hallux interphalangeal angle (normal 10 or less) 15 were measured on pre- and postoperative radiographs. Metatarsus adductus was measured radiographically (Fig. 8). The technique used for measurement relates the position of the metatarsals relative to the midfoot; a normal value is 15 or less, mild adductus is 16 19, moderate is 20 25, and severe is more than STATISTICAL ANALYSIS Descriptive and comparative statistical analysis was performed using Instat software. Standard chi-square analysis was performed on continuous variables. Pearson and binary correlation coefficients were used to evaluate the noncontinuous data, and positive coefficients closer to 1 indicate strong correlation and values closer to 0 indicate weak or no correlation. RESULTS Demographic and Historical Data Hallux rigidus was associated with a positive family history, bilateral involvement, and female gender (Table 4). Overall, 87 of 110 patients (79%) had bilateral

5 Foot & Ankle International/Vol. 24, No. 10/October 2003 HALLUX RIGIDUS 735 Fig. 3: A, Curved MTP joint articulation. B, Chevron-shaped joint articulation. C, Flat MTP joint articulation.

6 736 COUGHLIN AND SHURNAS Foot & Ankle International/Vol. 24, No. 10/October 2003 Fig. 4: Radiograph of joint width measurement technique: A,APview;B, lateral view. See Appendix C for information on measurement technique. Fig. 5: Diagram demonstrating measurement of metatarsus primus elevatus 40, and metatarsal declination angle. 5 See Appendix D for information on measurement technique. disease clinically and radiographically at the final followup compared to 22 of 110 patients (19%) seen at the initial examination. In 74 patients with a positive family history, 95% (70/74 patients) had bilateral disease at the final follow-up. There was no statistically significant association between hallux rigidus and a history of trauma (p =.08). However, a history of trauma was common in patients who developed unilateral hallux rigidus (positive trauma history on the involved side in 18/23 (78%) patients with unilateral hallux rigidus). Eighteen of 110 patients (16%) stated that shoewear contributed to the hallux rigidus and 8 of 110 patients (7%) felt that their occupation contributed to the hallux rigidus. There was no statistically significant correlation between hallux rigidus and shoewear or occupation. (r =.08, p >.1). Fig. 6: First metatarsal protrusion distance. 36 See Appendix E for information on measurement technique. Examination Data There were 12 patients (12 feet) with pes planus noted on the Harris mat study and/or with excess heel valgus (Table 5). There were only four patients (four feet) who had less than or equal to 5 of ankle dorsiflexion with the knee fully extended and the foot held in a

7 Foot & Ankle International/Vol. 24, No. 10/October 2003 HALLUX RIGIDUS 737 Fig. 7: Angular measurements. 15 See Appendix F for information on measurement technique. neutrally aligned or slightly inverted position (two had pes planus and two had normal arch height); however, no subject had an Achilles or gastrocnemius contracture (<0 dorsiflexion) and no lengthening procedures were performed preoperatively or subsequently. There was no correlation between first ray mobility of more than 7 mm and hallux rigidus (r =.1, p =.7). The Fig. 8: Metatarsus adductus angle. 13 See Appendix G for information on measurement technique. mean first ray mobility was 5.4 mm (only one patient had as much as 10 mm). Similarly, there was no correlation between first ray mobility and elevatus. Radiographic Data Preoperatively, 15/127 feet (12%) had a hallux valgus angle of more than 15 and 1 2 intermetatarsal angle of more than 9, but only two patients (two feet) had concurrent symptomatic hallux rigidus and hallux Table 4: Demographic data Patients Female Age at Age at Duration Family Trauma Total Onset Surgery Symptoms History History (mean) (mean) (years) (patients) (patients) Number (13 70) (16 76) (1 30) Table 5: Physical examination data Exam Item MTP Joint MTP Joint Ankle Pes Planus Heel Valgus First Ray Dorsiflexion ( ) Total Dorsiflexion ( ) (Harris mat) (>6 ) Mobility (mm) Motion ( ) Mean preoperative No cases of No symptomtic Not recorded No clinical value ( 15 to 45) (5 80) contracture cases record Mean follow-up patients 10 patients 5.4 value (0 65) a (0 110) a (5 20) (9%) (9%) (3 10) Total number of patients = 110. a Cheilectomy patients only.

8 738 COUGHLIN AND SHURNAS Foot & Ankle International/Vol. 24, No. 10/October 2003 Table 6: Mean radiographic findings X-Ray Value Metatarsus primus elevatus First metatarsal declination angle Hallux valgus angle 1 2 intermetatarsal angle Joint width Findings (based on 127 feet) 5.4 mm (0 10) 21.4 (15 30 ) 12.2 (0 20 ) 7.6 (2 14 ) 1.3 mm ( mm) Sclerosis 2.2 (0 3) Hallux interphalangeal angle Metatarsus adductus angle Sesamoid changes Metatarsal protrusion angle 17.9 (5 30 ) 13.2 (5 25 ) 38-irregular, 40-cystic, 49-normal 0.54 mm ( 6 to5 mm) valgus (Table 6). The hallux interphalangeal angle (HIPA) averaged 17.9 overall and there were only 13 of 127 feet (10%) that had a normal HIPA of 10 or less. There was a correlation between an increase in the HIPA and a decrease in the hallux valgus (HVA) and the 1 2 intermetatarsal angle (r = 0.4, p =.04). The mean metatarsus adductus angle (MAA) was less than 15 (13.2 overall), but 22/127 (17%) feet had a MAA of 16 19, 15/127 (12%) feet had a MAA of 20 25, and none had a greater than 25 (severe) MAA. Preoperatively, 38 feet had irregular sesamoids, 40 had cystic sesamoids, and 49 had no obvious sesamoid abnormality. Twenty-one MTP joints were noted to have a loose body on preoperative radiographs and corresponding findings at the time of surgery, but on final follow-up radiographs, no loose bodies were noted. There was significant progression in postoperative periarticular sclerosis (difference in the means of 2.2, p =.0001) of the MTP joint and loss of the MTP joint width (difference in the means of 1.3, p =.0001). Furthermore, there was correlation between loss of MTP joint width and MPE as well as increased sclerosis (r =.5, p =.01). Of the 110 patients, 25 had chevron, 56 flat, and 29 oval-shaped MTP joints. For individual patients, joint shapes were the same on both feet and thus 81/110 (74%) had a flat or chevron-shaped MTP joint (flat and chevron shape with preoperative hallux rigidus, r =.5, p =.05). However, there was no correlation of joint shape with HVA or 1 2 intermetatarsal angle (r =.1, p =.3). Of the 127 feet studied preoperatively, 36 first metatarsals (28%) were 1 mm or longer compared to the second metatarsal, 51 (40%) were of equal length, and 40 (32%) were shorter than the second metatarsal. MPE Data There was a correlation between the 1-MDA and MPE (r =.6, p =.03). One hundred seventeen of 127 preoperative feet (92%) had radiographic measurements for MPE that were within a normal range (8 mm or less) and 10 of 127 feet had up to 10 mm MPE preoperatively. There were no patients with Grade 0 hallux rigidus, six with Grade 1, 32 with Grade 2, 34 with Grade 3, and 8 with Grade 4. Grade 4 patients had significantly more MPE compared to Grade 1. Moreover, there was a correlation between loss of MTP joint motion (dorsiflexion and total motion) and MPE (r =.6, p =.05) (Table 7). Pathology Pathologic specimens of the MTP joint were routinely sent before 1988 and all 33 pathologic specimens of the MTP joint were consistent with osteoarthritis. DISCUSSION History and Demographics The common findings of patients with hallux rigidus, including pain with first MTP motion, restricted first MTP motion, dorsal bony proliferation at the first MTP joint, Table 7: Metatarsus primus elevatus and grade of hallux rigidus a Grade Number of MPE MTP MTP Patients Dorsi- Total flexion ( ) Motion ( ) (0 8) (0 8) (0 9) (5 10) a Preoperative measurements for patients undergoing cheilectomy.

9 Foot & Ankle International/Vol. 24, No. 10/October 2003 HALLUX RIGIDUS 739 intolerance of constricting shoes, inability to rise up on toes, and a supinated or everted gait, 25,27,42,48,49 were verified in the current study. Family History Bonney and MacNab 3 reported that patients with a positive family history of great toe arthritis had an earlier onset of disease. We found no association with the age of onset of disease and positive family history; hallux rigidus was associated with a positive family history of great toe problems in almost two-thirds of patients. Age Goodfellow 32 and Jack 41 stated that hallux rigidus started spontaneously in childhood or adolescence and Nilsonne 54 suggested that hallux rigidus be categorized as either primary (adolescent) or secondary (adult). However, in review of several studies on hallux rigidus that report on age, 22,25,28,29,34,44,47,49,56,67 the mean age at onset was 51 years. Only a handful of series have reported on adolescent patients with hallux rigidus. 2,41,42,50 The mean age at onset in the current study was 43 years (range, years); only six patients developed symptoms at an age of less than 20 years and only two patients had cheilectomies before age 20 (age 16 and 17). Moreover, Bingold 2 reported that pathologic specimens from both adult and adolescent patients with hallux rigidus were consistent with degenerative arthritis, a finding consistent with the current study. We believe that dividing patients artificially into primary and secondary categories is unnecessary given the small number of adolescent patients and the fact that all patients appear to have the same degenerative process. Bilateral Involvement With the passage of time, a high percentage of patients will exhibit bilateral disease. As Gould 33 observed, at the time of treatment often only one side is severe enough to require surgery. Gender Predilection In an early report, it was observed 4 that twothirds of patients surgically treated for hallux rigidus patients were females. Conversely Gould 33 reported that 64% (27/42 patients) were males and that gender predilection depended on age. We reviewed 18 studies of patients with hallux rigidus in which gender was recorded 22,25,28,29,33,34,39,44,47 50,53,54,67 and found that 394/643 patient were females (62%), a percentage comparable to the current study. We found no association between age and gender, except that females were more commonly affected in all age groups. Pes Planus Pes planus as a cause of hallux rigidus has been implicated in several studies 2,7,9,11,22,27,30,41,51,54,60,68 but no demographic data were reported in any of these studies to substantiate the notion. Harris and Beath 37 reported on 3619 normal military recruits and noted that 15% of the patients had an asymptomatic depression of the longitudinal arch. Eleven percent of patients in the present series had pes planus based on either a positive Harris mat study and/or excess heel valgus, a incidence surprisingly consistent with that previously reported by Harris and Beath. 37 Achilles Tendon Contracture Isolated gastrocnemius tightness has recently been reported to occur in up to 24% of normal patients when defined as less than 5 dorsiflexion with the knee fully extended. 21 In the same report, isolated gastrocnemius tightness was implicated in the pathogenesis of midfoot, hindfoot, and forefoot pathology. 21 Bingold 2 suggested an association of hallux rigidus and Achilles tendon contracture. Our data do not support either notion. There were only four patients who had 5 of dorsiflexion with the knee fully extended and the foot in a neutral alignment (two with pes planus and two with normal arch height). RADIOGRAPHIC DATA Associated Hallux Valgus Nilsonne 54 proposed that the development of hallux valgus precluded the development of hallux rigidus. The incidence of concurrent hallux valgus and rigidus has been reported to vary from 15 to 100%. Clinically there were only two cases of symptomatic/concurrent hallux valgus and hallux rigidus in this series. The concurrent presentation of hallux valgus and hallux rigidus was not common (12%). Hallux Valgus Interphalangeus Sorto et al. 65 hypothesized an inverse relationship between HVA and HIPA, concluding that an increased HVA indicated MTP joint instability while a decreased angle indicated stability. The normal value was reported to be 5 5 and in subjects with hallux rigidus a mean hallux valgus interphalangeus angle of 15 was reported. 5,65 We found a correlation between a greater HIPA and diminished HVA or 1 2 intermetatarsal angle, confirming Sorto s findings. We hypothesize that as the MTP joint becomes more resistant to transverse plane deformity, this predisposes to an increased HIPA. Metatarsal Articular Shape The association of a flat or chevron-shaped distal metatarsal articular surface with hallux rigidus has been hypothesized by several authors, 24,44,48 although we do

10 740 COUGHLIN AND SHURNAS Foot & Ankle International/Vol. 24, No. 10/October 2003 not know the incidence of occurrence in the general population. Schweitzer et al. 61 observed no difference in MTP joint shape between patients with hallux rigidus and hallux valgus. With the passage of time and the increasing severity of hallux rigidus, obvious flattening or widening of the articular surface, 22,27,35,54,60 occurs which has been attributed to periarticular osteophyte formation. 1,47 50 DuVries 24 and others 48,49 hypothesized that a rounded or oval joint was less stable and thus more prone to the development of hallux valgus, but that a flat or chevron-shaped joint was more stable and prone to hallux rigidus. We found no correlation between joint shape and the HVA or the 1 2 intermetatarsal angle. There was a correlation between a flat and chevron-shaped joint and hallux rigidus in the present study and we suggest that such joint shapes resist transverse plane deformities and predispose to hallux rigidus. Metatarsus Adductus We hypothesized that metatarsus adductus may predispose to hallux rigidus. There was no statistically significant association between hallux rigidus and adductus (MAA); however patients with hallux rigidus in this series had a far greater incidence than the general population (0.1%). 70 We speculate that medial inclination of the forefoot may possibly increase transverse plane pressure on the medial aspect of the first MTP joint increasing the risk in these patients of hallux rigidus, although further long-term studies will be needed to evaluate this issue. Metatarsal Protrusion First Metatarsal Length A long first metatarsal 8,23,58,60,69 has been implicated in the development of hallux rigidus, but only a few studies have actually reported data on the comparative length of the first and second metatarsals. 3,5,22,41,53,61 Of the studies that reported data, the incidence of a long first metatarsal varied between 0 and 60% 3,22,41,49,53 ; however the method of measurement appears to influence the reported incidence of a long first metatarsal. The method used by Hardy and Clapham, 36 also used in this series, is not influenced by an increased 1 2 intermetatarsal angle or metatarsus adductus. In the current series, the incidence of occurrence of a long first metatarsal was no more common in patients with hallux rigidus than in a large group of asymptomatic military recruits studied by Harris and Beath. 38 There was no significant difference in metatarsal length between subgroups with hallux rigidus nor was there any correlation between increased first metatarsal length and hallux rigidus. Metatarsus Primus Elevatus The concept of MPE was introduced by Lambrinudi 45 in 1938 and endorsed in several reports, 3,6,7,9,10,22,29,41, 42,45,46,57,58 although definitive proof of this entity has not been confirmed. Radiographic evidence to the contrary 5,40,51 has been reported. Notions such as functional hallux limitus (reduction of first MTP joint dorsiflexion with simulated loading of the foot compared to passive MTP joint dorsiflexion) have also been proposed as a cause of hallux rigidus. 17,18 Based on the results of this study, there were 10 cases of up to 10 mm of MPE identified. However, it appeared that MPE was a secondary change as there was a correlation with advancing grade of hallux rigidus. We believe that elevatus is a secondary change resulting from an arthritic MTP joint and that the first ray elevation associated with radiographically advanced hallux rigidus is analogous to metatarsus primus varus in hallux valgus; as the bunion deformity progresses so does the 1 2 intermetatarsal angle, and similarly as hallux rigidus progresses so does the first ray elevation. However, treating elevatus with osteotomies appears to treat a secondary rather than a primary problem, and these osteotomies have been associated with difficult salvage procedures when they fail. 59 First Ray Hypermobility Several reports have suggested an association between first ray hypermobility and hallux rigidus, 2,6,33, 39,41,44,60 although specific measurement data were not reported to confirm any association. None of the previous studies used a measuring device to quantitate first ray mobility and only one of the studies reported on how hypermobility was indentified. 33 A recent report by Glasoe 31 found that measurements of first ray mobility with a device similar to the one used in this study 43 were far more reliable than manual (hand) measurement and questioned the validity of manual measurements altogether. We found no association between first ray hypermobility and hallux rigidus; the mean mobility was 5 mm in arthrodesis patients and 5.8 mm in cheilectomy patients. Both values are well below the quoted normal values of first ray mobility and if hypermobility of the first ray is defined as more than 8 9 mm 31,43 of dorsal excursion on the measuring device, then one first ray (that had 10 mm) was hypermobile (1/127). Transfer metatarsalgia or lesions may develop if hypermobility is present or if first ray weightbearing is avoided secondary to a painful MTP joint. 31,43 Nine patients had transfer lesions preoperatively. CONCLUSIONS Hallux rigidus was not associated with MPE, first ray hypermobility, increased first metatarsal length, Achilles or gastrocnemius tendon tightness, abnormal foot posture, symptomatic hallux valgus, adolescent

11 Foot & Ankle International/Vol. 24, No. 10/October 2003 HALLUX RIGIDUS 741 onset, shoewear, or occupation. Hallux rigidus was associated with hallux valgus interphalangeus, female gender, and a positive family history in bilateral cases. In most cases the problem was bilateral, the exceptions being when there was trauma involved. If trauma had occurred, then the problem was unilateral. Metatarsus adductus was more common in patients with hallux rigidus than in the general population but a significant correlation was not found. Additionally, a flat or chevron-shaped MTP joint was more common in hallux rigidus patients. APPENDICES Appendix A: Technique of Harris Mat Measurement The midline foot axis (MFA) is drawn from the center of the second toe imprint through the center of the heel imprint and the distal forefoot and posterior heel are marked on the line. 14,36 At the midpoint between these two marks a perpendicular line is drawn medial and lateral to the midline foot axis; 1 cm marks are labeled +1, +2, +3 for points medial to the axis, and 1, 2, 3 for points lateral to the axis. A low arch height stains medial (positive values) and a high arch height stains laterally (negative values). For staining between incremental marks, the greater value is chosen. Positive values indicate pes planus and negative values indicate pes cavus. Appendix B: Technique of First Ray Mobility Measurement The foot-plate and ankle foot orthoses secure the lateral foot and ankle leaving the first ray free for examination. 43 The first ray is grasped and translated in a dorsal/plantar direction and the excursion measured with the micrometer, which is placed on the first metatarsal head, just medial to the tendon of the extensor hallucis longus. 43 Appendix C: Technique of Measurement of Joint Space Width A, On the pre- and postoperative radiographs, three points were placed along the corresponding articular surfaces of the proximal phalanx base and distal metatarsal. On the AP radiograph, these points were placed at the medial, central, and lateral aspect of the joint surfaces. B, On the lateral radiograph, these points were placed at the dorsal, middle, and plantar aspect of the joint surface. On a perpendicular line connecting each pair of corresponding points, the joint width was measured in millimeters. The six scores were added and divided by six, giving an average joint width for each joint. Appendix D: Technique of Measurement of MPE MPE: On pre- and postoperative weightbearing lateral radiographs, a line is drawn along the distal dorsal metaphyseal cortex of the first and second metatarsals; a perpendicular line is drawn between the two cortical lines, and the difference between the dorsal cortices of the first and second metatarsals is measured in millimeters MDA: On the pre- and postoperative weightbearing lateral radiographs, the lateral longitudinal axis of the first metatarsal is drawn using mid-diaphyseal reference points. 5 A second line estimating the plantar surface of the foot is drawn intersecting reference points on the plantar aspect of the calcaneus and the medial sesamoid. The intersection of these two lines forms the first metatarsal declination angle (angle A). Appendix E: Technique of Measurement of First Metatarsal Protrusion Distance A transverse reference line is made by bisecting two points (one at the most lateral aspect of the calcaneocuboid joint and the other at the most medial aspect of the talonavicular joint). 36 The longitudinal axis of the second metatarsal is drawn using two metaphyseal-diaphyseal reference points 36 ; where the second metatarsal axis intersects the transverse reference line, this point acts as the center of rotation for this axis. The axis line is rotated medially and two arcs are drawn, one at the distal extent of the distal articular surface of the second metatarsal and one at the distal extent of the articular surface of the first metatarsal to measure the protrusion distance between the first and second metatarsals. A perpendicular line drawn between the two arcs is measured in millimeters. A positive value indicates that the first metatarsal is longer relative to the second, and negative values indicate that the first is shorter relative to the second metatarsal. Appendix F: Technique of Angular Measurements Mid-diaphyseal reference points are drawn for the proximal phalanx and first and second metatarsals. 15 The points are typically placed 1 2 cm from the distal or proximal articular surfaces, and connected by a longitudinal line forming the axis of the respective bone. In the case of the distal phalanx, a reference point is placed at the distal tip of the phalanx and at the midpoint of the articular surface of the distal phalanx. A line is drawn connecting these points, which forms the longitudinal axis of the distal phalanx. The intersection of this axis with the longitudinal axis of the proximal phalanx forms the hallux interphalangeal axis (HIPA) (angle A); the intersection of the longitudinal axes of the proximal phalanx and the first metatarsal

12 742 COUGHLIN AND SHURNAS Foot & Ankle International/Vol. 24, No. 10/October 2003 forms the hallux valgus angle (HVA) (angle B); the intersection of the longitudinal axes of the first and second metatarsals forms the 1 2 intermetatarsal angle (1 2 IMA) (angle C). Appendix G: Technique of Metatarsus Adductus Measurement A line is drawn on the lateral aspect of the foot between two points: the most lateral extent of the calcaneocuboid joint (CC) and the most lateral extent of the fifth metatarsocuboid joint (5MC). 13 A second line is drawn along the medial lesser tarsus connecting two more points: the most medial extent of the first metatarsocuneiform joint (1MC) and the most medial extent of the talonavicular joint (TN). A mark is made at the midpoints of these lines and a line connecting them is drawn bisecting the lesser tarsus. Finally, a line perpendicular to the lesser tarsus bisection line is drawn. 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