Heterotopic ossification after total ankle arthroplasty

Transcription

1 FOOT AND ANKLE after total ankle arthroplasty W. J. Choi, J. W. Lee From Yonsei University College of Medicine, Seoul, Korea We evaluated the incidence of heterotopic ossification following total ankle replacement to determine whether the degree of ossification was associated with the clinical outcome. We evaluated 90 ankles in 81 consecutive patients who underwent total ankle replacement, and heterotopic ossification was assessed according to proportional involvement of the ankle joint. Correlation analysis was used to investigate the association between heterotopic ossification and outcome. No significant association was found between the formation of heterotopic ossification and the clinical outcome. The degree of heterotopic ossification in the posterior ankle joint was not significantly correlated with posterior ankle pain (p = 0.929), the American Orthopaedic Foot and Ankle Society score (p = 0.454) or range of movement (p = 0.283). This study indicates that caution should be observed in attributing symptoms and functional limitation to the presence of heterotopic ossification in the posterior ankle joint when considering excision of heterotopic bone after total ankle replacement. W. J. Choi, MD, Assistant Professor J. W. Lee, MD, PhD, Professor Yonsei University College of Medicine, Department of Orthopaedic Surgery, 50 Yonsei-ro, Seodaemun-gu, Seoul , Korea. Correspondence should be sent to Professor J. W. Lee; ljwos@yuhs.ac 2011 British Editorial Society of Bone and Joint Surgery doi: / x.93b $2.00 J Bone Joint Surg Br 2011;93-B: Received 25 May 2011; Accepted after revision 8 July 2011 Common symptoms after total ankle replacement (TAR) include pain, located particularly medially and posteriorly, and functional disabilities such as difficulty rising from a seat, climbing stairs and walking downhill. 1-7 However, the cause of these symptoms is unclear. Two common radiological findings at follow-up are osteolysis and heterotopic bone formation, which may be implicated as possible aetiological factors. Although osteolysis is a significant problem after TAR, 8-11 the natural history and clinical significance of the heterotopic ossification that develops after TAR have not been fully investigated. The goal of our study was to review pre- and post-operative radiographs to assess the incidence and aetiology of heterotopic ossification after TAR and its association with the outcome. We hypothesised that there would be no relationship between the formation of heterotopic ossification and outcome. Patients and Methods A total of 112 ankles in 103 patients who underwent TAR by a single surgeon (JWL) between 2004 and 2009 were retrospectively assessed. A total of 22 ankles were excluded because the follow-up was less than 24 months, leaving 90 ankles in 81 patients with a mean clinical and radiological followup of 44.8 months (24 to 77) for analysis. The HINTEGRA (Newdeal SA, Lyon, France) total ankle system was used in all patients. The mean age of the patients was 64 years (33 to 84). A total of 48 TARs were undertaken in men and 42 in women; three men and six women underwent bilateral TAR (Table I). The operation was performed for osteoarthritis in 35 ankles, traumatic arthritis in 46 and rheumatoid arthritis in nine. The study was approved by the hospital s institutional review board. Operative technique. The technique of TAR has been previously described. 10 A tourniquet around the thigh was used in each case and was inflated to 320 mmhg and deflated before closure to ensure adequate haemostasis. Bone cutting guides were used to prepare the tibia and talus. Care was taken to remove any loose bone fragments, followed by copious irrigation to remove any debris. In order to restore neutral alignment and correct ligament instability or bony deformity, various additional procedures were performed according to the treatment algorithms of our institution: 10 deltoid ligament release in 44 ankles, percutaneous Achilles tendon triple hemisection lengthening 12 in 29, calcaneal valgus osteotomy in six, peroneus longus tendon transfer to peroneus brevis in six, gastrocnemius recession in six, modified Broström procedure 13 in five, dorsiflexion osteotomy of the first metatarsal bone in four, 1508 THE JOURNAL OF BONE AND JOINT SURGERY

2 HETEROTOPIC OSSIFICATION AFTER TOTAL ANKLE ARTHROPLASTY 1509 Table I. Descriptive summary of the characteristics of the patients (ankles) (Mann-Whitney U test) Absent (n = 59) Present (n = 31) p-value Clinical factors Male:female ratio 26:33 22: Mean age (yrs) (range) 64.4 (33 to 84) 63.3 (47 to 78) Mean weight (kg) (range) 66.8 (46 to 97) 68.9 (46 to 90) Mean body mass index (kg/m 2 ) (range) 26.3 (18 to 33) 25.5 (20 to 30) Pre-operative diagnosis (n, %) Degenerative osteoarthritis 24 (40.7) 11 (35.5) Post-traumatic osteoarthritis 27 (45.8) 19 (61.3) Rheumatoid arthritis 8 (13.6) 1 (3.2) Takakura classification 15 (n, %) Stage 3 20 (33.9) 6 (19.4) Stage 4 39 (66.1) 25 (80.6) Table II. Classification of heterotopic ossification in total ankle replacement Grade 0 Grade 1 Grade 2 Grade 3 Grade 4 Radiological findings No ossification Ossification is detectable behind the distal aspect of the tibia but not in the ankle joint space Ossification from distal aspect of the tibia, with < 50% of the joint space Ossification from distal aspect of the tibia, with > 50% of the joint space, but no radiographic bridge Ossification that bridges the space and lengthening of the tibialis posterior tendon in one. Non-steroidal anti-inflammatory drugs (NSAIDs) were not routinely prescribed post-operatively and their use was not monitored in the outpatient setting. In uncomplicated cases a short-leg cast was applied for four weeks. When additional procedures had been required a short-leg cast was applied for a maximum of six weeks. The patients were allowed to gradually return to full weightbearing and pre-operative activities as tolerated. Clinical evaluation. Clinical assessment included the American Orthopaedic Foot and Ankle Society (AOFAS) anklehindfoot score. 14 Pain was graded according to a visual analogue scale (VAS: 0, no pain; 10, maximum pain). The active range of dorsiflexion and plantar flexion was recorded in degrees. The relationship between the incidence of post-operative heterotopic ossification and possible causative factors, including age, body weight, body mass index (BMI), diagnosis and the Takakura classification 15 of arthritis of the ankle, the pre-operative presence of osteophytes posteriorly in the ankle joint, peri-operative release of medial ligaments, and pre-operative serum calcium and alkaline phosphatase (ALP) levels, was also investigated. The mean duration of surgery was also recorded based on the tourniquet time. Radiological evaluation. Standardised weight-bearing anteroposterior and lateral radiographs obtained by tangential fluoroscopy were taken post-operatively at six weeks, three months, six months, one year and two years. was graded based on the filling of the space between the inferior border of the tibial component and the superior border of the posterior talar process as described in Table II. The appropriateness of tibial component sizing in relation to the prepared tibia was assessed by the distance between the posterior edge of the tibial component and the posterior cortex of the distal tibia, as measured on a lateral radiograph. When the component was smaller than the cut surface of the tibia, the distance was recorded as a negative number. In order to assess the relationship between the incidence of heterotopic ossification and tibial component cover, the relationship between the size of the tibial component and the tibial cut surface was stratified as small (< -2 mm), optimal (-2 mm to 2 mm), and large (> 2 mm). Statistical analysis. Categorical variables were compared using the chi-squared test, and continuous variables were compared using a Mann-Whitney U test. Correlations between the extent of heterotopic ossification and the clinical outcome were determined using Spearman s correlation coefficient. A p-value < 0.05 was considered statistically significant. Data were analysed using the software package SPSS for Windows version 18.0 (SPSS Inc., Chicago, Illinois). Results Of the 90 ankles, 31 (34.4%) showed radiological evidence of heterotopic ossification, comprising grade 1 in eight ankles, grade 2 in 14, grade 3 in eight and grade 4 in one (Fig. 1). The ossification was always located posterior to the tibial component and was first indentified postoperatively at three months in eight ankles, six months in nine, one year in 13 and two years in one. When early postoperative radiographs were compared with those obtained at least two years later, the grade had increased in seven ankles. There was no significant difference in the mean duration of follow-up in patients with and without heterotopic ossification (44 months (25 to 62) versus 45 months (24 to 64), respectively) (Mann-Whitney U test, p = 0.798). None of the pre-operative characteristics of the patients were associated with the development of heterotopic ossification: age, p = 0.606; body weight, p = 0.351; BMI, p = 0.208; diagnosis, p = 0.717; and Takakura classification, 15 p = 0.221; (all Mann-Whitney U tests), although heterotopic ossification was more than twice as prevalent in men as in women (p = 0.025; Table I). At the most recent follow-up the mean range of movement was not significantly different in patients with and without heterotopic ossification: dorsiflexion, p = 0.283; and plantar flexion, p = 0.406; (both Mann-Whitney U tests) (Table III). VOL. 93-B, No. 11, NOVEMBER 2011

3 1510 W. J. CHOI, J. W. LEE Fig. 1a Fig. 1b Fig. 1c Fig. 1d Fig. 1e Radiographs showing the classification of heterotopic ossification posterior to the distal tibia on lateral radiographs of the ankle, in a) grade 0, no ossification; b) grade 1, ossification detectable behind the distal aspect of the tibia but not in the ankle joint space (eight ankles); c) grade 2, ossification from the distal aspect of the tibia with < 50% of the joint space (14 ankles); d) grade 3, ossification from the distal aspect of the tibia, with > 50% of the joint space but no radiological bridging (eight ankles); and e) grade 4, ossification that bridges the space (one ankle). Nor was there a significant difference in the mean post-operative VAS for pain (p = 0.929) or AOFAS scores (p = 0.454). There was no significant association between the degree of heterotopic ossification and clinical outcome (VAS, AOFAS score and range of movement; p > 0.05; Table IV). There was no significant relationship between the incidence of heterotopic ossification and the pre-operative presence of osteophytes in the posterior ankle joint, surgical release of the medial ligament, duration of surgery, or serum calcium and ALP levels (Table V). In terms of the size matching of the tibial component to the cut surface, ten components (11.1%) were small, 79 (87.7%) were optimal and one (1.2%) was large. The presence of heterotopic ossification was not significantly associated with tibial component cover in any of the component size categories (p = 0.565; Table VI). Discussion is fairly common after total hip and knee replacement, 16,17 with a reported incidence ranging between 2% and 90% but severe functional loss only affects between 1% and 2% of patients. 18 The incidence of ossification after TAR also varies greatly between 7% and 64%, 6,10,19-23 but the literature contains little information about its natural history and clinical significance. Some reports have suggested it as a source of pain. 6,20,21 Valderrabano, Hintermann and Dick 6 observed heterotopic ossification in 43 of 68 ankles (63%) after implanting the STAR prosthesis (Waldemar Link GmbH & Co. KG, Hamburg, Germany) despite the post-operative use of prophylaxis. Excision of the ossification and arthrolysis was necessary in 21%. 6 Elsewhere, symptomatic heterotopic ossification was detected in five of 67 HINTEGRA TARs (7%), causing pain and stiffness. 24 Removal of the ossification was undertaken in two ankles with a good result. However, Kim et al 10 reported that 11 of 45 ankles (24%) undergoing HINTEGRA TAR had heterotopic ossification, but found no significant difference in clinical outcome between patients with and without ossification. These patients were asymptomatic and no excision was THE JOURNAL OF BONE AND JOINT SURGERY

4 HETEROTOPIC OSSIFICATION AFTER TOTAL ANKLE ARTHROPLASTY 1511 Table III. Comparison of clinical outcome for the patients with and without heterotopic ossification. Mean values (SD) (Mann-Whitney U test) Outcome * Absent (n = 59) Present (n = 31) p-value Pre-operative ROM (12.59) (13.91) Dorsiflexion 7.12 (6.53) 5.00 (4.83) Plantar flexion (8.91) (10.75) Post-operative ROM (14.69) (13.75) Dorsiflexion (7.72) (7.87) Plantar flexion (9.85) (9.62) Pre-operative VAS 7.38 (1.54) 7.17 (1.53) Post-operative VAS 3.11 (2.17) 3.06 (2.29) Pre-operative AOFAS score (12.93) (10.48) Post-operative AOFAS score (12.57) (8.74) * ROM, range of movement; VAS, visual analogue scale; AOFAS, American Orthopaedic Foot and Ankle Society Table IV. Results of correlation analyses between the degree of heterotopic ossification and clinical outcomes Outcome * Correlation coefficient p-value VAS AOFAS ROM * VAS, visual analogue scale; AOFAS, American Orthopaedic Foot and Ankle Society; ROM, range of movement Spearman s correlation coefficient necessary. Wood and Deakin 22 found heterotopic ossification in 94 of 200 ankles (47%), with no association between its presence and pain. In our study the overall incidence of ossification was 34.4%. Except for gender, no preoperative characteristics were associated with the development of heterotopic ossification, men having a markedly higher incidence of ossification after TAR in this study (p = 0.025). When heterotopic ossification developed it was always located posterior to the distal tibia. It seems likely that disturbance of the cortex and periosteum by the distal tibial osteotomy is an important initiator for the development of ossification, owing to the release of mesenchymal stem cells and osteoblasts. 25 In addition, heterotopic ossification was present on the one-year post-operative radiographs in 30 of the 31 affected ankles. Among these 30 ankles, only seven had a subsequent increase in the grade of ossification. This is similar to the behaviour of the heterotopic ossification that occurs after total hip and knee replacement. 26,27 The range of movement, post-operative pain and AOFAS scores were not statistically different in patients with or without heterotopic ossification. Soft-tissue trauma is associated with the formation of heterotopic ossification, 17,27 which might be related to the excision of osteophytes in the posterior ankle joint or medial ligament release. However, in our study the risk of heterotopic ossification did not appear to Table V. Relationship between the incidence of heterotopic ossification and pre-operative osteophyte formation, peri-operative medial ligament release, tourniquet time and serum calcium and alkaline phosphatase levels (Mann-Whitney U test) Absent (n = 59) Present (n = 31) p-value Posterior osteophyte (n, %) 21 (35.6) 15 (48.4) Medial ligament release (n, %) 28 (47.4) 17 (54.8) Tourniquet time (min) (SD) (23.81) (33.15) Serum Ca * level (mg/dl) (SD) 9.24 (0.57) 9.16 (0.65) Serum ALP level (IU/L) (SD) (23.18) (19.90) * Ca, calcium ALP, alkaline phosphatase Table VI. Analysis for the relationship between tibial component coverage and the occurrence of heterotopic ossification Tibial component Grade of heterotopic ossification cover Small (< -2 mm) 0/10 (0) 1/10 (10) 3/10 (33.3) 0/10 (0) 1/10 (10) Optimal (-2 mm to 2 mm) 0/79 (0) 7/79 (8.9) 11/79 (13.9) 7/79 (8.9) 0/79 (0) Large (> 2 mm) 0/1 (0) 0/1 (0) 0/1 (0) 1/1 (100) 0/1 (0) increase after these interventions. In addition, an increase in serum calcium and ALP levels has been related to heterotopic ossification after total hip replacement, 28,29 but there was no significant association between serum calcium and ALP levels and ossification in our study. Furthermore, several studies have demonstrated that the prophylactic use of NSAIDs or radiotherapy reduces the incidence of heterotopic ossification after arthroplasty of the hip. 25,30 Patients in this study were not routinely given prophylactic NSAIDs post-operatively and were not monitored for possible NSAID use. Several limitations of this study should be noted. The first involves the selective use of the HINTEGRA system, as our findings might not be applicable to patients receiving other implants. Secondly, as heterotopic ossification involves a three-dimensional structure, measuring the volume of heterotopic bone would have been a better way to quantify ossification. However, measuring the volume with plain radiographs was not practical. Instead, we used our classification system, which adjusts for differences in the scale of ossification between patients and takes into account the proportional involvement of the posterior ankle joint space. We believe that assessing the degree of ossification using this classification system was sufficient to achieve the goals of this study. Our study confirmed our hypothesis that heterotopic ossification formation is not associated with the outcome after TAR, and that the correlation between the degree of ossification and the outcome is not high in patients undergoing TAR. Our findings indicate that despite the fact that heterotopic ossification formation is not uncommon after VOL. 93-B, No. 11, NOVEMBER 2011

5 1512 W. J. CHOI, J. W. LEE TAR, the causative factors of posterior ankle pain and functional limitation remain to be determined. Surgeons should be cautious in attributing posterior symptoms and functional disabilities to the presence of heterotopic ossification in the posterior ankle joint when considering its excision. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. References 1. Bonnin MP, Judet T, Colombier JA, et al. Midterm results of the Salto Total Ankle Prosthesis. Clin Orthop 2004;424: Bonnin MP, Laurent JR, Casillas M. Ankle function and sports activity after total ankle arthroplasty. Foot Ankle Int 2009;30: Knecht SI, Estin M, Callaghan JJ, et al. The Agility total ankle arthroplasty: seven to sixteen-year follow-up. J Bone Joint Surg [Am] 2004;86-A: Kopp FJ, Patel MM, Deland JT, O'Malley MJ. Total ankle arthroplasty with the Agility prosthesis: clinical and radiographic evaluation. Foot Ankle Int 2006;27: San Giovanni TP, Keblish DJ, Thomas WH, Wilson MG. Eight-year results of a minimally constrained total ankle arthroplasty. Foot Ankle Int 2006;27: Valderrabano V, Hintermann B, Dick W. Scandinavian total ankle replacement: a 3.7-year average followup of 65 patients. Clin Orthop 2004;424: Valderrabano V, Pagenstert G, Horisberger M, Knupp M, Hintermann B. Sports and recreation activity of ankle arthritis patients before and after total ankle replacement. Am J Sports Med 2006;34: Hanna RS, Haddad SL, Lazarus ML. Evaluation of periprosthetic lucency after total ankle arthroplasty: helical CT versus conventional radiography. Foot Ankle Int 2007;28: Kadoya Y, Kobayashi A, Ohashi H. Wear and osteolysis in total joint replacements. Acta Orthop Scand Suppl 1998;278: Kim BS, Choi WJ, Kim YS, Lee JW. Total ankle replacement in moderate to severe varus deformity of the ankle. J Bone Joint Surg [Br] 2009;91-B: Koivu H, Kohonen I, Sipola E, et al. Severe periprosthetic osteolytic lesions after the Ankle Evolutive System total ankle replacement. J Bone Joint Surg [Br] 2009;91- B: Kim BS, Lee JW. Total ankle replacement for the varus unstable osteoarthritic ankle. Techniques in Foot & Ankle Surgery 2010;9: Broström L. Sprained ankles. VI: surgical treatment of chronic ligament ruptures. Acta Chir Scand 1966;132: Kitaoka HB, Alexander IJ, Adelaar RS, et al. Clinical rating systems for the anklehindfoot, midfoot, hallux, and lesser toes. Foot Ankle Int 1994;15: Takakura Y, Tanaka Y, Kumai T, Tamai S. Low tibial osteotomy for osteoarthritis of the ankle: results of a new operation in 18 patients. J Bone Joint Surg [Br] 1995;77- B: Iorio R, Healy WL. after hip and knee arthroplasty: risk factors, prevention, and treatment. J Am Acad Orthop Surg 2002;10: Toyoda T, Matsumoto H, Tsuji T, Kinouchi J, Fujikawa K. after total knee arthroplasty. J Arthroplasty 2003;18: Berry DJ, Garvin KL, Lee SH, et al. Hip and pelvis reconstruction. Illinois: American Academy of Orthopaedic Surgeons, 1999: Buechel FF Sr, Buechel FF Jr, Pappas MJ. Twenty-year evaluation of cementless mobile-bearing total ankle replacements. Clin Orthop 2004;424: Buechel FF Sr, Buechel FF Jr, Pappas MJ. Eighteen-year evaluation of cementless meniscal bearing total ankle replacements. Instr Course Lect 2002;51: Lee KB, Cho SG, Hur CI, Yoon TR. Perioperative complications of HINTEGRA total ankle replacement: our initial 50 cases. Foot Ankle Int 2008;29: Wood PL, Deakin S. Total ankle replacement: the results in 200 ankles. J Bone Joint Surg [Br] 2003;85-B: Barg A, Elsner A, Hefti D, Hintermann B. Total ankle arthroplasty in patients with hereditary hemochromatosis. Clin Orthop 2010;469: Bai LB, Lee KB, Song EK, Yoon TR, Seon JK. Total ankle arthroplasty outcome comparison for post-traumatic and primary oseoarthritis. Foot Ankle Int 2010;31: Pellegrini VD Jr, Evarts CM. Radiation prophylaxis of heterotopic bone formation following total hip arthroplasty: current status. Semin Arthroplasty 1992;3: Frassica FJ, Frassica DA, Berry DJ. Ectopic bone. New York: Churchill Livingstone, 1996: Rader CP, Barthel T, Haase M, Scheidler M, Eulert J. after total knee arthroplasty: 54/615 cases after 1-6 years' follow-up. Acta Orthop Scand 1997;68: Kjaersgaard-Andersen P, Pedersen P, Kristensen SS, Schmidt SA, Pedersen NW. Serum alkaline phosphatase as an indicator of heterotopic bone formation following total hip arthroplasty. Clin Orthop 1988;234: Ahrengart L, Lindgren U. Functional significance of heterotopic bone formation after total hip arthroplasty. J Arthroplasty 1989;4: D'Lima DD, Venn-Watson EJ, Tripuraneni P, Colwell CW. Indomethacin versus radiation therapy for heterotopic ossification after hip arthroplasty. Orthopedics 2001;24: THE JOURNAL OF BONE AND JOINT SURGERY