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Hip International / Vol. 12 no. 4, 2002 / pp. 383-387 Early resection of heterotopic ossification after total hip arthroplasty: A review of the literature Department of Orthopedics and Traumatology, Ghent University Hospital, Gent - Belgium ABSTRACT: Early excision of heterotopic ossification was performed in 8 patients at an average of 10.2 months after total hip arthroplasty. All patients received a single irradiation dose of 7Gy the day before the operation, followed by oral indomethacin (3x25mg/day) for six weeks. Continuous passive mobilization under epidural anesthesia was started imme- diately post-operatively. At an average follow-up of 2 years none of them had radiograph- ic or clinical evidence of recurrence. Consequently we recommend resection as soon as there are severe clinical implications, even when bone scans indicate immaturity of the het- erotopic ossification and provided that the resection is combined with proper non-surgical treatment consisting of irradiation and oral indomethacin and immediate extensive reha- bilitation program. (Hip International 2002; 4: 383-7) KEY WORDS: Heterotopic ossification, Resection, Total hip arthroplasty mine whether these patients would benefit from ear- ly resection of the peri-articular ossification with a Currently resection of heterotopic ossification (HO) proper and reliable postoperative strategy to prevent is generally suggested after complete maturation (be- recurrence of HO with clinical implications. tween 14-18 months), since earlier intervention is thought to predispose to recurrence (1-3). Reliable indicators of maturation of HO are diminishing activity on seri- al bone scans and/or decreasing levels of alkaline phos- phatase (1, 4). However, most literature reports deal At the orthopedic department of Ghent University with treatment of HO of the hip associated with trau- Hospital, a series of 8 patients (7 men, 1 woman) un- matic brain injury or spinal cord injury, with an im- derwent resection of HO of the hip. All patients had portant correlation between the severity of the neu- previously undergone THA. There were no patients rologic lesion and the recurrence of HO (5-9, 32-34).
with traumatic brain or spine injury. Their mean age Nevertheless, HO after primary total hip arthroplasty was 37.7 years, ranging between 31 and 75 years. All (THA) is a relatively common complication occurring patients had pain and restriction of motion. Three hips in 20 to 90 percent of all cases. Although usually asymp- were ankylotic with an average flexion contracture of tomatic, heterotopic bone formation can cause ma- 27 degrees (ranging between 20 and 30 degrees) and jor disability consisting of pain and a decreased range the other five were restricted with an average of 43 of motion in up to 7 percent of patients undergoing degrees of hip flexion (ranging between 30 and 50 de- THA (10). Therefore, it would be interesting to deter- grees) and an average flexion contracture of 18 Early resection of heterotopic ossification after THA TABLE I - AVERAGE HIP MOTION BEFORE AND AFTER RESECTION OF HO
TABLE II - AVERAGE HARRIS HIP SCORE BEFORE
fects. One patient received additional stomach pro- tection. Rehabilitation was started the same day as the operation, consisting of continuous passive mo- bilization for up to 5 hours a day under continuous epidural anesthesia for several days to allow an im- degrees (ranging between 0 and 20 degrees). Abduction averaged 14 degrees (ranging between 0 and 40 de- The mean interval between the previous hip surgery grees), adduction 6 degrees (ranging between 0 and and the resection of HO was 10.2 months, ranging 20 degrees), external rotation 2 degrees (ranging be- between 7 and 14 months. According to Brooker’s tween 0 and 10 degrees) and internal rotation was 0 classification, 5 joints were classified as Class III and degrees in those 5 joints (Tab. I). As all patients un- 3 joints as Class IV. Although none of the patients un- derwent resection within 14 months post-operative- derwent serial bone scans, the single bone scan showed ly, we considered the HO to be immature in all cas- an increased uptake in 6 patients. At the time of re- es, although some of them did not have a positive section, alkaline phosphatase was elevated in 3 pa- bone scan or elevated alkaline phosphatase. All op- tients. The functional results were evaluated by erations were performed by the same senior surgeon.
means of the Harris Hip Score (HHS) (11). The mean A combined anterolateral and posterolateral ap- HHS (Tab. II) was 54 (ranging between 40 and 67) pre- proach in lateral decubitus was used for all patients operatively and 91, six weeks post-operatively rang- in order to obtain a good visualization of the HO. Full ing between 81 and 100. The average motion post- resection of the HO and capsule was performed up operatively (Tab. I) was 92 degrees of flexion (rang- to normal anatomical landmarks which are more eas- ing between 80 and 105 degrees), 0 degrees of ex- ily recognized because of the presence of the pros- tension in all patients, 31 degrees of abduction (rang- thesis, in contrast to when a wedge resection is per- ing between 30 and 40 degrees), 26 degrees of ad- formed after brain and spinal injuries. If necessary duction (ranging between 15 and 30 degrees), 26 de- psoas and external rotators were sectioned. In some grees of external rotation (ranging between 20 and 45 cases part of the HO was left in place to reduce the degrees) and 19 degrees of internal rotation (ranging risk of fracture of the greater trochanter and to guar- between 10 and 30 degrees). At an average follow- antee normal function of the abductor musculature.
up of 2 years (6 months up to 3 years), the mean HHS There were no lesions of the ischial nerve post-op- (Tab. II) was 91 (ranging between 81 and 100) with an eratively. All patients received a single dose of ra- average motion (Tab. I) of 99 degrees of flexion (rang- diotherapy (7 Gy) the day before the operation and ing between 70 and 125 degrees), 0 degrees of ex- oral indomethacin was started post-operatively for 6 tension in all patients, 32 degrees of abduction (rang- weeks (3 x 25mg/24hours). None of the patients had ing between 30 and 40 degrees), 25 degrees of ad- to discontinue the indomethacin because of side-ef- duction (ranging between 20 and 30 degrees), 29 Fig. 1 - Radiographic image before resection.
Fig. 2 - Radiographic image 6 weeks after resection.
degrees of external rotation (ranging between 20 and to be successful without recurrence provided that it 40 degrees) and 21 degrees of internal rotation (rang- is combined with appropriate non-surgical treatment.
ing between 15 and 25 degrees). No important clini- In our series this consisted of a single irradiation cal or radiographic recurrence of periarticular ossifi- dose pre-operatively, complemented with oral in- cation has been seen up to now (Fig. 1, 2, 3). One pa- domethacin therapy for six weeks after the excision.
tient even had a dislocation one year after resection At an average follow-up of two years after resection, caused by squatting during gardening as he had over there seems to be no loss of the initially gained mo- tion and functional result. The risk of severe HO af- ter THA is higher in patients who have developed HO after previous surgery, in men with hypertrophic os- teoarthrosis and in patients with ankylosing spondyli- tis or diffuse idiopathic skeletal hyperostosis (12-14).
Despite early resection of the HO, none of our pa- Other possible predisposing factors include exten- tients have had a recurrence so far. Although a long- sive intra-operative bleeding with hematoma, post- term follow-up is lacking and our series is small, we operative infection, operative approach with trocha- believe that early resection of HO after THA is likely nteric osteotomy, or dislocation of the prosthesis dur- Early resection of heterotopic ossification after THA up to 5 years (20-23). Serial 99m-Tc-MDP bone scans are felt to be the most sensitive instrument for diag- nosing early HO and assessing HO maturity (1, 5, 24).
The correlation between post-operative alkaline phosphatase levels and maturity of HO in THA remains unclear (1, 5, 18, 25). Garland’s study on resection of HO showed that normal bone scans, alkaline phos- phatase levels, and mature roentgenographic appearance of HO were unreliable predictors of recurrence (26).
Radiation in combination with resection has been re- ported to reduce the risk of recurrence (27). The suc- cess of irradiation lies in the inhibition of cellular pro- liferation and differentiation in the formation of os- teoid (28). Schmidt et al emphasized the prophylac- tic effect of indomethacin in a placebo-controlled clin- ical study (29). According to the studies by Sodemann et al, NSAIDs inhibit the migration and differentiation of mesenchymal cells which are responsible for HO formation (30). Commonly reported postoperative com- plications are delayed wound healing, excessive bleeding, superficial and deep infection, fractures, in- juries to the ischial nerve and recurrence of HO (27, 32-34). Frischhut et al (31) and Freebourn et al (5) re- ported good results following early removal of HO with- out waiting for bone maturation. Wick et al reported on their series of 21 patients who underwent surgi- cal excision of HO at an average of 5.5 months after primary hip surgery, followed by oral indomethacin therapy. They did not find a higher recurrence rate of HO and therefore concluded that it is not absolutely Fig. 3 - Radiographic image 21 months after resection.
necessary to use bone scans to assess the maturity of HO (15). In summary we think that resection of HO ing the first post-operative week (15-17). According after THA is recommended as soon as there is im- to the critical review by Shaffer, most of the present portant disability, provided that surgery is preceded concepts regarding the time of HO resection arise from by a single irradiation dose and followed by oral in- studies of spinal cord injured patients, suggesting a domethacin therapy for several weeks in order to pre- minimum of 14 months for maturation, with most pa- vent recurrence of HO. Obviously, further study on tients requiring 18 months or longer (2). Concerning larger series and longer follow-up periods are manda- HO after THA, most authors agree that it will be ra- diographically evident by 3 months postoperatively but may be visible as early as 2-3 weeks (18, 16, 19, 20). Although the ectopic bone continues to mature, many reports suggest that there is no change in ei- ther the volume or the distribution of HO after 6 months (16, 18). Others describe HO formation as an ongo- ing dynamic process, with changes in the amount and distribution occurring up to one year, and in one study, 18. Mollan RAB. Serum alkaline phosphatase in heterotopic para-articular ossification after hip replacement. J BoneJoint Surg 1979; 61 B: 432-4.
1. Tibone J. Heterotopic ossification around the hip in spinal 19. Nolan MB. Complications of total hip arthroplasty treat- cord-injured patients. J Bone Joint Surg (Am) 1978; 60: ed by reoperation. J Bone Joint Surg (Am) 1975; 57-A: 2. Wharton G. Heterotopic ossification. Clin Orthop 1975; 20. Sundaram NA. Heterotopic bone formation following total hip arthroplasty in ankylosing spondylitis. Clin Or- 3. Morgan Th. The treatment of ankylosis of the hip joint secondary to heterotopic ossification. J Bone Joint Surg 21. Shaffer B. A critical review. Heterotopic ossification in total hip replacement. Bull Hosp Jt Dis Orthop Inst 1989; 4. Tanaka T. Quantitative assessment of para-osteo- arthropathy and its maturation on serial radionuclide 22. Kromann-Andersen C. Ectopic bone formation follow- bone images. Radiology 1977; 123: 217-21.
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