NON-CONSTRAINED TITANIUM-POLYETHYLENE TOTAL ENDOPROSTHESIS IN THE TREATMENT OF HALLUX RIGIDUS A prospective clinical 2-year follow-up study

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1 Scandinavian Journal of Surgery 91: , 2002 NON-CONSTRAINED TITANIUM-POLYETHYLENE TOTAL ENDOPROSTHESIS IN THE TREATMENT OF HALLUX RIGIDUS A prospective clinical 2-year follow-up study P. Ess, M. Hämäläinen, J. Leppilahti Department of Surgery, Oulu University Hospital, Oulu, Finland ABSTRACT Background and Aims: To evaluate the outcome in a prospective 2-year follow-up study of a non-constrained titanium-polyethylene total endoprosthesis (ReFlexion ) in the treatment of hallux rigidus. Material and Methods: Ten patients with painful hallux rigidus were treated with a non-constrained titanium-polyethylene total endoprosthesis (ReFlexion ). The American Orthopaedic Foot and Ankle Society (AOFAS) scoring was used preoperatively and at follow-up. Results: At 2-year follow-up, the AOFAS scoring showed 5 instances of excellent, 1 of good, 2 of fair, and 2 of poor outcome. Eight patient were subjectively satisfied and 2 dissatisfied. Five of the patients were painless, 4 had mild, occasional pain, and 1 had moderate, daily pain in the first metatarsophalangeal joint. The mean VAS was 7.6 (SD 2.0) preoperatively and 1.1 (SD 1.4) at 2-year follow-up (p < 0.001). Extension increased by a mean of 25 (13 38) degrees and flexion by a mean of 15 (2 35) degrees (p < 0.001). Eight patients had no activity limitations, while 1 had mild and 1 moderate limitations. Alignment of the metatarsophalangeal joint was good in 7 cases, but some degree of valgus malalignment was seen in 2 and symptomatic malalignment in 1. Complications included one subluxation of a prosthesis, one recurrence of severe valgus alignment and one superficial wound infection. Radiological loosening of one cementless phalangeal component was seen at follow-up. Conclusion: The non-constrained titanium-polyethylene total arthroplasty gave satisfactory 2-year outcome in 60 % of the patients. It is an alternative treatment for hallux rigidus in low demand patients. We do not recommended it for athletes and young people, because high forces acting on the prosthesis may cause a failure. Key words: Hallux rigidus; arthroplasty; metatarsophalangeal endoprosthesis; non-constrained endoprosthesis Correspondence: Juhana Leppilahti, M.D. Department of Surgery Oulu University Hospital PL 22 FIN Oulu, Finland juhana.leppilahti@oulu.fi

2 Non-constrained titanium-polyethylene total endoprosthesis in the treatment of hallux rigidus 203 INTRODUCTION All prostheses that are used for MTP-I joint replacement in hallux rigidus are designed to relieve pain, to restore a functional range of motion, to correct existing and to prevent further deformity, and to give cosmetic improvement. Many prostheses have been used in an attempt to achieve all these aims since the first prosthesis was implanted over 40 years ago. The prostheses can be divided into four basic designs: silastic hemiprosthesis, silastic hinged prosthesis, metal hemiprosthesis and non-constrained metal-polyethylene total endoprosthesis. Silastic hemiprostesis often leads to mechanical failure and a painful, swollen joint and does not give an acceptable outcome compared to the other forms of treatment (1, 2, 3). The initial reports of the silastic hinged prosthesis were promising (4, 5, 6), but long-term results showed that the implants are not durable and often lead to mechanical failure and stiffness of the joint, even when the subjective result is good (7, 8, 9). Erosion and abrasion of the prosthesis may lead to bone resorption, silicone synovitis and lymphadenitis (1, 8). The development of a non-constrained metal-polyethylene total endoprosthesis began in the late 1970 s. Johnson and Buck (10) reported a good 3.5- year follow-up outcome with a stainless steel-polyethylene total endoprosthesis (De Puy ). The development of titanium-polyethylene total endoprostheses began in the late 1980 s, and the first reports are promising (11, 12, 13). Many previous studies of replacement arthroplasty are retrospective and report only subjective results. The major problem has been the lack of a universally accepted rating system for forefoot surgery. The lack of a universal, consistent protocol for subjective and objective evaluation of hallux rigidus has also prevented any direct comparison of the results in MTP I joint endoprosthesis surgery. The American Orthopaedic Foot and Ankle Society (AOFAS) has published a rating system, which is considered as a consensus score in forefoot surgery and includes evaluation of pain, function and alignment (14, 15). We describe a prospective 2-year follow-up study of a non-constrained titanium-polyethylene total endoprosthesis (ReFlexion ) in the treatment of hallux rigidus using AOFAS scoring preoperatively and at follow-up. PATIENTS AND METHODS PATIENTS The study population comprised 10 successive patients operated on for hallux rigidus using the Reflexion total endoprosthesis at Oulu University Hospital. The etiology of hallux rigidus was degenerative osteoarthrosis in 7 cases, rheumatoid arthritis in 2 and trauma in 1. Nine of the patients were female and 1 was male, their mean age being 53 (range 44 77) years. The indications for the procedures were pain and stiffness of the first metatarsophalangeal joint, which had not been responsible to NSAID medication and resulted in the restriction of activity. None of the patients had had a previous operation on the first metatarsophalangeal joint. Pain was moderate in 5 of the patients and severe in 5 (Table 1). Activity limitations were mild in 1 patient, moderate in 6 and severe in 3. None of the patients were capable of using fashionable, conventional shoes. Metatarsophalangeal joint motion was moderately restricted in 1 patient and severely restricted in 9. Alignment was good in 5 patients, while some degree of hallux malalignment was observed in 4 and severe malalignment in 1. METHODS The operation was performed under spinal anaesthesia with tourniquet hemostasis. The metatarsophalangeal joint was exposed through a medial approach. Approximately 4 5 mm of bone was removed from the distal part of the metatarsal head and 3 mm from the phalangeal base with an oscillating saw. The guide pin was driven into the metatarsal canal by means of an alignment guide. The starter reamer (4.5 mm) was driven over the guide pin into the metatarsal canal up to approximately 45 mm. The small reamer was then driven over the guide pin to the same depth as the starter reamer. The small cone reamer guide was inserted into the reamed cylindrical canal and slide over the stem of the cone reamer guide, and cone reaming was performed. The diameter could then be expanded, if desired, up to medium or large. In phalangeal preparation, the guide pin was driven into the shaft of the proximal phalanx. The proximal phalanx was reamed with the starter cylindrical reamer placed over the guide pin. With the small phalangeal reamer, the base of the proximal phalanx was reamed to the desired depth. The diameter of the cone could then be increased by using medium or large phalangeal reamers. With the use of a base planer, excess bone around the opening of the cone was removed. Using metatarsal and phalangeal trials the joint was checked for range of motion and stability. If desired, greater dorsiflexion might be accomplished by reaming deeper on either the metatarsal or the phalangeal side of the joint. The final implants were inserted without cement, with the exception of one distal component, which was cemented. Antibiotic solution was used to irrigate the wound and to soak the prosthesis before implantation. Hallux valgus was corrected by appropriate suturing of the soft tissues, usually plication of the medial part of the joint capsule. If the sesamoids were immobile, they were released but not excised. Postoperatively, the first 2 patients were treated for 3 weeks with a heel shoe. One prosthesis subluxated during the 3 weeks, and we modified the postoperative regimen so that orthosis or a soft cast splint was used for 3 weeks, after which physiotherapy was begun, including active and gentle passive range of motion exercises for the joint. Full weight bearing was permitted at 3 weeks. Clinical and x-ray evaluations were performed 2, 6, 12 and 24 months postoperatively. AOFAS scoring was analysed preoperatively and at 2-year follow-up. This scoring assesses pain (0 40 points), function (0 45 points) and alignment (0 15 points). STATISTICAL ANALYSIS The statistical analyses were performed with the SPSS software (SPSS Inc, Chicago, IL). Student s t-test was used to calculate the differences between the means and the chisquared test to calculate the differences between the frequencies. P-values of less than 0.05 were considered significant.

3 204 P. Ess, M. Hämäläinen, J. Leppilahti TABLE 1 Preoperative data and 2-year follow-up results of MTP I replacement arthroplasty. Points Preoperative 2-year follow-up Number of Number of patients patients (N =10) (N =10) Pain (40 points) None Mild, occasional Moderate, daily Severe almost continuous Function (45 points) Activity limitations No limitations No limitation of daily activities, such as employment responsibilities, limitation of recreational activities Limitation of daily and recreational activities Severe limitation of daily and recreational activities Footwear requirements Fashionable, conventional shoes, no insert required Comfort footwear, shoe insert Modified shoes or brace MTP joint motion (extension plus flexion) Normal or mild restriction (75 or more) Moderate restriction (30 74 ) Severe restriction (less than 30 ) IP joint motion (plantar flexion) No restriction Severe restriction (less than 10 ) MTP-IP stability (all directions) Stable Definitely unstable or able to dislocate Callus related to hallux MTP-IP No callus or asymptomatic callus Callus, symptomatic Alignment (15 points) Good, hallux well aligned Fair, some degree of hallux malalignment Observed, no symptoms Poor, obvious symptomatic malalignment TABLE 2 Preoperative scoring and 2-year follow-up outcome. Outcome Preoperative 2-year follow-up Number of patients Number of patients (N =10) (N =10) Excellent (100 93) 0 5 Good (92 83) 0 1 Fair (82 66) 0 2 Poor (less than 65) PAIN RELIEF The mean VAS was 7.6 (SD 2.0) preoperatively and 1.1 (SD 1.4) at 2-year follow-up (p < 0.001). Initially, 5 MTP I joints were moderately and 5 severely painful. At follow-up, 5 MTP I joints were not painful, while 4 were mildly and 1 moderately painful. The causes of pain were subluxation of the prosthesis in one case, loosening of a distal component in one case and recurrent hallux valgus in one case. RANGE OF MOTION RESULTS OUTCOME According to the AOFAS performance score at 2-year follow-up, five patients had excellent, one good, two fair, and two poor results. The AOFAS performance score increased from a mean value of 41 (20 63) preoperatively to a mean value of 83 (52 95) at 2-year follow-up (p < 0.001, Table II). At the time of follow-up, the mean arch of flexion extension was 55 (34 73) degrees, an increase by a mean of 40 (27 66) degrees compared to the preoperative value (Table I). Extension increased by a mean of 25 (13 38) degrees and flexion by a mean of 15 (2 35) degrees. IP joint motion was normal in all cases at follow-up. There was a significant increase in flexion and extension compared to the preoperative value (p < 0.001).

4 Non-constrained titanium-polyethylene total endoprosthesis in the treatment of hallux rigidus 205 A C B D Radiographic findings of a 46-year-old female with hallux rigidus in the right foot. Fig. 1A, B. Preoperative AP and lateral views showing gradus III finding in the MTP I joint. 1C, D. AP and lateral views two months after Reflexion -arthroplasty. STABILITY Preoperatively, none of the patients reported any subjective sensation of instability or demonstrated any objective instability. At follow-up, the distal component of one endoprosthesis subluxated plantarly, causing a moderate limitation in flexion-extension. The recurrent valgus malalignment caused a mild activity limitation. FOOTWEAR REQUIREMENTS None of the patients were able to use fashionable shoes preoperatively, whereas 7 were able to use such shoes at follow-up. No callus was related to hallux MTP-IP joint preoperatively or at follow-up. ALIGNMENT Initially, the MTP I alignment was normal in 5 cases, while mild hallux valgus malalignment was present in 4 and severe malalignment in 1. At follow-up, the alignment was normal in 7cases, while mild valgus malalignment had recurred in 2 and severe valgus in 1 of the patients. RADIOGRAPHIC ASSESSMENT Radiologic loosening was defined as a radiolucent line of more than two millimeters. One cementless distal component was radiologically loose. All metatarsal implants were fixed without cement and showed no evidence of loosening. COMPLICATIONS There were two major complications and one minor complication. One prosthesis subluxated in the plantar direction in the early postoperative period. At follow-up, the MTP I joint was quite stiff, but not painful, and there are therefore no plans for reoperation. One severe hallux valgus malalignment recurred and was recently treated with removal of the prosthesis and arthrodesis of the MTP I joint using free bone transplantation. One minor complication was a superficial wound infection, which improved with antibiotic treatment.

5 206 P. Ess, M. Hämäläinen, J. Leppilahti DISCUSSION The main finding in the present study was, that the 2-year outcome was successful only in 6/10 patients, and there were also 2 poor result. Five patients with an excellent outcome were painless, the prosthesis did not cause any activity limitations, and the MTP I joint motion had increased significantly, although the range of motion was moderately restricted compared to the normal contralateral hallux. These patients had no shoe problems and no callus related to the hallux, and the joint was stable and the hallux in good alignment. The causes of the two poor outcomes were one recurrent valgus deformity and one subluxated endoprosthesis. The strength of this study was the prospective study design, where AOFAS-scoring was used preoperatively and in a follow-up. The weaknesses of the study were a small sample size, a short followup time, and a heterogenous patient selection including 7 patients with primary osteoarthritis, 2 patients with rheumatoid arthritis and one posttraumatic hallux rigidus. We found only three previous reports of non-constrained titanium-polyethylene total arthroplasty in the treatment of hallux rigidus. Koenig (11) reported successful 3-year follow-up results in 9/10 revision arthroplasties, where a damaged silastic implant had been replaced with a titanium-polyethylene total endoprosthesis. Koenig et al. (12) further published the 5-year follow-up results of 61 Biomet Total Toe prostheses in 59 patients, reporting 84 % to have excellent results according to the Koenig scoring. Four prostheses were revised because of pain, malalignment or limited function. Lu et al. (13) reported variable 5-year follow-up results with 22 titanium-polyethylene prostheses. 73 % had successful results, but 27 % were revised. There are many factors that affect the outcome of joint-implanted arthroplasty. These include the preoperative state of the foot, patient selection, implant design and the duration of follow-up (16). The most important factors to influence the outcome are the preoperative state of the MTP I joint and the foot. This includes the condition of the stabilising structures, the controlling tendons and the adjacent joints. Appropriate suturing of the soft tissues, plication of the medial part of the joint capsule, additional osteotomies, extensor tendon z-lengthening, and release or removal of the sesamoids may be needed. In rheumatoid patients, the condition of the other MTP joints and phalanges may require surgery before the implant surgery. In the present series, no additional osteotomies or extensor tendon lengthening were not needed. The selection of patients is important. MTP I joint arthroplasty is indicated in low-demand patients, and it is not recommended for athletes and young people, because high forces acting on the prosthesis may cause a failure. A better range of motion is often achieved in well-motivated patients with a high pain threshold and elastic skin with a slight tendency to scar formation. The outcome is also affected by the type of operation (primary or secondary) and the cause of pathophysiology (inflammatory, posttraumatic or degenerative). For instance, in the comparison of the series of Granberry et al. (8) and Cracchiolo et al. (9) with hinged silastic implants of the MTP I joint, one important explanation for the different outcomes and controversial conclusions was the selection of patients. In the latter series, 57 % of the patients had a diagnosis of rheumatoid arthritis compared to 23 % in the former. In the present series, 2/10 patients had a diagnosis of rheumatoid arthritis. All of our arthroplasties were primary operations. Implant design also has an effect on the outcome. The disadvantages of silastic implants include prosthesis fractures, silicone-induced synovitis and osteolysis (1, 8, 17). Ris et al. (7) reported prosthesis fractures in 57 % of 53 Swanson implants at 4-year follow-up. In the series of Granberry et al. (8), prosthesis fractures were seen in 29 % of 90 prostheses at 3- year follow-up. Verhaar et al. (1) reported osteolysis in over 50 % of 58 patients with Swanson implants at 5-year follow-up. However, there is often a discrepancy between encouraging subjective results and the failure of the silastic implant. One explanation may be that the silastic implant remains intact long enough for fibrotic tissue to form, whereafter the biomechanics of the joint are dictated by this fibrous tissue. The follow-up was short in the present study. Although short follow-up studies can help to identify certain problems with a prosthesis, longer follow-up studies are essential to evaluate a the prosthetic design, since a reduction in the range of motion, recurrence of deformity, bone resorption and even a fracture of the implant may well occur long after the implantation. To sum up, a non-constrained titanium-polyethylene arthroplasty gave successful outcome only for 6/10 patients with painful hallux rigidus. We do not recommended it for athletes and young people, because high forces acting on the prosthesis may cause a failure. The arthroplasty is indicated only in lowdemand patients. In the future, controlled, randomised studies between between implant arthroplasty, arthrodesis and excision arthroplasty are needed. REFERENCES 0 1. Verhaar J, Bulstra S, Walenkamp G: Silicone arthroplasty for hallux rigidus. Implant wear and osteolysis. 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6 Non-constrained titanium-polyethylene total endoprosthesis in the treatment of hallux rigidus Ris H-B, Mettler M, Engeloch F: Langzeitergebnisse mit der Silastic-Endoprothese nach Swanson am Grosszehengrundgelenk. Disrepans zwischen Klinik und radiologischem Befund. Zeitsch Orthop 1988;126: Granberry WM, Noble PC, Bishop JO, Tullos HS: Use of a hinged silicone prosthesis for replacement arthroplasty of the first metatarsophalangeal joint. J Bone Joint Surg Am 1991;73: Cracchiolo A, Weltmar JB, Lian G, Dalseth T, Dorey F: Arthroplasty of the first metatarsophalangeal joint with a doublestem silicone implant. J Bone Joint Surg Am 1992;74: Johnson KA, Buck PG: Total replacement arthroplasty of the first metatarsophalangeal joint. Foot Ankle 1981;1: Koenig RD: Revision arthroplasty utilizing the Biomet Total Toe system for failed silicone elastomer implants. J Foot Ankle Surg 1994;3: Koenig RD, Horwitz LR: The Biomet Total Toe system utilizing the Koenig score: A five-year review. J Foot Ankle Surg 1996;35: Lu HS, Kou BL, Yan YL: Follow-up result of 14 cases of the first metatarsophalangeal joint arthroplasty with titanium total joint prosthesis. (in Chinese) Chung Hua Wai Ko Tsa Chic 1994;32: Kitaoka HB, Alexander IJ, Adelaar RS, Nunley JA, Myerson MS, Sanders M: Clinical rating systems for the ankle-hindfoot, midfoot, hallux, and lesser toes. Foot Ankle 1994;7: Schneider W, Knahr K: Scoring in forefoot surgery. A statistical evaluation of single variables and rating systems. Acta Orthop Scand 1998;69: Shereff MJ, Baumhauer JF: Hallux rigidus and osteoarthrosis of the first metatarsophalangeal joint. Current concepts review. J Bone Joint Surg Am 1998;80: Shereff MJ, Jahss MH: Complications of silastic implant arthroplasty in the hallux. Foot Ankle 1980;1: Received: July 30, 2001 Accepted: February 1, 2002