Tibial lengthening for unilateral Crowe type-IV developmental dysplasia of the hip.

BACKGROUND: Developmental dysplasia of the hip (DDH) is associated with chronic pain and limping which especially has a negative impact on the patients' daily activities, body image, and self-esteem. Although total hip arthroplasty remains the first choice for treatment of DDH in adults, minimally invasive alternative approaches are being increasingly favored both by the surgeon and the patients with severe DDH. This study aimed to evaluate the outcome of these patients treated with a mono-lateral external fixator-based tibial lengthening procedure.
MATERIALS AND METHODS: During the period of month between June 1999 and January 2006, 13 (mean ages 20.8 years) adult patients with unilateral Crowe type-IV DDH were treated by tibial lengthening using a mono-lateral external fixator over an intramedullary nail. Bone healing, infection, gait correction and improvement in body image were assessed during postoperative followup. Patients' overall health status at the end of followup was assessed using the short form-36 (SF-36) health survey.
RESULTS: Patients were followed up for an average of 7.3 years. Successful bone healing was observed in all 13 patients and no further surgeries were indicated. A mean external fixation index of 12.4 days/cm was achieved. Bone formation fell in good to excellent categories with a mean consolidation index of 50.1 days/cm. Pin-tract infections were observed in two patients. The degree of limping was reduced from severe or moderate preoperatively to mild postoperatively. Neither equinus deformity nor painful degenerative osteoarthritis and hip dysfunction were observed in any of the patients studied. The SF-36 questionnaire survey showed that all patients were satisfied with their outcomes.
CONCLUSIONS: Tibial lengthening may effectively correct gait and satisfactorily improve body image in young patients with unilateral Crowe type-IV DDH. Mono-lateral external fixator allows for accelerated postoperative rehabilitation and optimal preservation of ankle movements. Lengthening along with intramedullary nails may significantly reduce the external fixation time and the risk of fixator-related complications.

INTRODUCTION

Developmental dysplasia of the hip (DDH) is a spectrum of anatomic abnormalities in the hip joint. Although DDH is most often present at birth, it may also develop during early childhood. According to the classification system proposed by Crowe et al.,1 DDH can be classified into four subtypes (I, II, III and IV), ranging from slightly dysplastic and concentrically located hips to severely dysplastic and completely dislocated hips with the femoral head in the false acetabulum.2 In unilateral Crowe type-IV DDH, chronic pain, limping gait and degenerative osteoarthritis-associated hip dysfunction are the major clinical manifestations, which have significant negative impacts on patients’ daily physical activities, body image, and self-esteem.3456

Currently, total hip arthroplasty (THA) remains the first option of reconstructive therapy for Crowe type-IV DDH. However, THA in DDH is a complex procedure with technical challenges on both the acetabular and femoral sides. Moreover, complications such as recurrent dislocation, osteolysis and loosening are not uncommon in these patients. Before the appearance of pain and hip dysfunction, poor body image and limping may be the main complaint in patients with unilateral Crowe type-IV DDH,6 especially in young, unmarried patients. Therefore, minimally invasive alternatives are highly desirable for these patients who intend to improve body image and limping gait.

Callus distraction, based on Ilizarov's principle of “tension stress,”6 is one such alternative and has gained popularity in treating various types of nonunions and deformities in recent years. We have previously reported successful applications of mono-lateral external fixator-based callus distraction in treating patients with nonunion and limb length discrepancy.78910 It has been documented that callus distraction using a mono-lateral external fixator on an intramedullary nail [Figure 1] has several advantages such as reduced time length of external fixation, increased patient comfort during the procedure and accelerated postoperative rehabilitation.11 The aim of this study was to evaluate the effectiveness of tibial lengthening using a mono-lateral external fixator over an intramedullary nail in treating limp and improving body image in young patients with unilateral Crowe type-IV DDH.

Figure 1

A clinical photograph showing mono-lateral external fixation

MATERIALS AND METHODS

A total of 13 patients with Crowe type-IV DDH underwent tibial lengthening using a mono-lateral external fixator over an IM nail between June 1999 and January 2006. The inclusion criteria include: (1) significant limping with psychological discomfort; (2) remarkable leg length discrepancy (LLD) >4 cm; (3) absence of pain or hip dysfunction. Patients with diabetes mellitus, liver cirrhosis, and HIV were excluded.

Preoperative evaluation

Prior to the surgical procedure, clinical examinations were performed on all subjects to evaluate the degree of limp, LLD and the range of motion (ROM) of the ankle. More specifically, limping gait was categorized into four grades based on the assessment system recommended by the American Academy of Orthopedic Surgeons/Hip Society: (1) none, no limp; (2) mild, detected by a trained observer; (3) moderate, detected by the patient; (4) severe, markedly altered or slow gait. To assess the required lengthening length, radiographs of the hip were taken (anteroposterior [AP] and lateral), according to which the planes of the osteotomies and the length and diameter of the intramedullary nails were determined [Figure 2a].

Figure 2

(a) Preoperative radiograph of pelvis showing both hip joints (anteroposterior view) in a 19-year old girl showing Crowe type-IV developmental dysplasia (case 1). (b) Postoperative radiograph of whole leg with ankle joint anteroposterior view showing corticotomy at the upper metaphysis of the tibia and a two segment mono lateral external fixation over an intramedullary nail with proximal locking. (c) Radiograph during the callus distraction. (d) Radiograph at the end of distraction (after removal of external fixation) distal locking was inserted. (e) Anterioposterior radiograph showing good bone consolidation at final followup. (f) Standing clinical photograph of patient at the end of followup. (g) Squatting clinical photograph of patient at the end of followup

Mono lateral external fixation

A two-segment mono-lateral external fixator (Third Medical Instrument Company, Wujin, China) was used in tibial lengthening [Figure 1]. This was a stable rectangular plane fixator with two screw rods and two link rails. With this two-segment fixator, the lengthening device could be easily adjusted in three steps: (1) the press boards (used to make the fixation more stable) were removed; (2) the middle hole of link rails was rotated clockwise (every half a circle equals 1 mm of lengthening); (3) the press boards were locked back to stabilize the external fixator.

Tibial lengthening procedure

The procedure was performed as we described in our previous reports.9 In brief, under the guidance of an intraoperative C-arm, an intramedullary nail was temporarily inserted first. Next pins were inserted at right-angles to the anatomical axis of the tibia beyond the nail respectively, above and below the position predefined for osteotomy. The intramedullary nail was then removed. The tibial shaft was exposed subperiosteally and a transverse osteotomy performed at the predefined point. The nail was then reinserted and secured proximally with a locking screw. The periosteum was sutured and the wound closed with drainage. A 2 cm gap was provided between the fixator and the thigh to allow for possible postoperative swelling. The distal locking screw was placed 2-3 cm away from the pins [Figure 2b].

Postoperative protocol

Broad-spectrum antibiotics were given intravenously to all patients postoperatively for a course of 7 days. Patients were encouraged to start partial weight-bearing and physical exercises on postoperative day 2. Callus distraction was started on postoperative day 7 at a rate of 1.0 mm per 24 h [Figure 2c].

All patients were followed up at the outpatient unit of our department. Both AP and lateral views of plain X-ray were done every 15 days to assess new bone formation, alignment of tibial shaft and the position and loosening of pins. When the required length was achieved, Distal locking screws were inserted into the nail and the external fixator was removed to facilitate unrestricted rehabilitation [Figure 2d]. The time to remove the intramedullary nail was dependent on when a sufficient consolidation was obtained (at least three cortices observed in plain X-ray examination). At each followup examination, the duration of the external fixation, external fixation index (the duration of external fixation in days per centimeter of distraction), and radiographic consolidation index (days until radiographic bone consolidation per centimeter of distraction) and complications (if any) were documented.

Evaluation criteria

The primary outcome measures of this study were bone union, infection, deformity and LLD. These were assessed based on a modified version of functional scoring system of the Association for the Study and Application of the Method of Ilizarov.11 Four categories of bone results were accordingly defined: (1) Excellent: Bone union, no infection, deformity of <7° and length discrepancy of <2 cm in the femur; (2) good: Union plus any two of the others; (3) fair: Union plus one of the others; and (4) poor: Nonunion or refracture or infection.

Functional results were based on six criteria: Amount of lengthening achieved, range of ankle movements, pain, gait, lateral tibial angle and the ability to perform activities of daily living. Four grades were classified according to the described criteria: Excellent, good, fair, and poor. An excellent result was an active individual with none of the other four criteria; good with one or two of the other four criteria, fair with three or four of the other criteria and poor was an inactive individual regardless of the other criteria. Short form-36 (SF-36) health survey questionnaire was used to assess the life quality of patients preoperatively and postoperatively.

RESULTS

A total of 13 patients met the inclusion criteria and were included in this study. Of them, 84.6% (11/13) were females. The mean age of the 13 subjects was 20.8 (18-27) years. The LLD was 4.53 cm (4-5.5 cm) [Table 1].

Table 1

Preoperative data with Crowe type-IV DDH (n=13)

Patients were followed up for an average of 7.3 years (4.1-11.3 years). There were no losses to followup. Bone healing was observed in all 13 patients at the lengthening area with no deformity or infection [Figure 2e]. The average durations of external fixation were 62.8 days (54-80 days), the mean external fixation indexes were 12.4 days/cm (12.0-15.6 days/cm). The average consolidation time and index was 226.7 days (180-289 days) and 50.1 days/cm (40.1-66.4 days/cm), respectively. According to the modified ASMAI, the results of bone outcome were excellent in nine patients and good in four patients. The results of functional outcome were excellent in 11 patients and good in two patients [Table 2].

Table 2

Postoperative data of Crowe type-IV DDH (n=13)

Pin-tract infections were observed in two cases. These responded to oral antibiotics. Aseptic pin loosening and re-fracture of the lengthening callus was not observed. No patient had proximal migration of the femoral head. No equinus deformity was observed. All patients had full range of ankle joint movements at the end of followup [Figure 2f and g]. Signs of hip joint osteoarthritis (e.g. pain and hip dysfunction) were not observed in any of the patient [Table 2].

Short form-36 questionnaire survey showed significant improvement in all parameters assessed. Whole body pain and mental problems were observed in two patients preoperatively and postoperatively [Table 3]. Given the significant improvement in body image and limping as well as restoration of normal daily activities, all patients were highly satisfied and comfortable with the procedure.

Table 3

Preoperative and postoperative data of SF-36 questionnaire

DISCUSSION

Crowe type-IV is the most severe type of DDH, where joint capsule and soft tissues around the hip become thickened, leading to contracture and abductor dysfunction of the gluteus medius.1213 As a result, THA, which is regarded as the gold standard of DDH treatment, is often indicated.1415 Due to a lack of normal stress stimuli, dysplasia is prominent both in the true acetabulum and the proximal femur. The true acetabulum is small and shallow with periacetabular, osteoporosis and small diameter or femoral head with or without adeformity of the proximal femur.13 All these factors mean difficulties and complications of THA for Crowe type-IV DDH. Generally speaking, severe pain and hip dysfunction resulting from osteoarthritis of the false acetabulum influences patients’ daily life and work and is regarded as a surgical indication for THA in Crowe type-IV DDH.131415

Before the hip becomes painful and dysfunctional, patients with unilateral Crowe type-IV DDH have significant complaints of body appearance and altered gait with a limp. Neglected, patients with DDH usually suffer severe pain and hip dysfunction due to the onset of osteoarthritis in later stages. However, THA is not a first choice for young, unmarried patients who mainly complaint of poor body image and a limp.16 Leg lengthening can theoretically relocate the focus of body weight backwards to the central line by pelvic rebalance and thus delay the onset of osteoarthritis. In our study, no signs of osteoarthritis such as pain and dysfunction of hip were observed during the entire followup. The study of Bhave et al.,17 showed that leg lengthening could significantly improve limping gait. In their study, the gait parameters including the mean stance time and second peak, normalized symmetry of quantifiable stance were improved obviously after leg lengthening. In our study, improvements in body image and limping were also observed postoperatively in all patients [Table 2].

Schiedel et al.,18 showed that femur lengthening may result in a higher cumulative organ dose which meant higher radiogenic risks to patients compared with tibial lengthening. Moreover, tibial lengthening has no interference on the structure of the hip joints and can preserve the ROM of hip without any obstacle to a future THA procedure. In our study, we, therefore, did tibial lengthening instead of femoral lengthening and satisfactory outcomes of function were achieved in all patients.

Huang et al.,19 described a technique for reducing limping by tibial lengthening along nails in adult patients with unilateral Crowe type-IV DDH. The Taiwanese team reported 17 cases of unilateral Crowe type-IV DDH treated with tibial lengthening. Good results were reported except that four patients had a 5° loss of ankle joint motion. In their study, the authors used the conventional (Ilizarov) ring external fixator so that the extensive physical therapy for restoring ankle joint motion could not start until the removal of the external fixator (about 2 months postoperatively). Compared with conventional ring type fixators, the mono-lateral fixators eases the patients in daily life and a moderate range of joint motion is allowed postoperatively because of the low number of muscular transfixations.20 Eralp et al.,21 demonstrated in their study that the incidence of joint stiffness and pain were higher in the ring external fixator group when compared to the uniplanar group for lengthening. In our department, good results were achieved in fields of long bone nonunion and limb deformity after using the mono-lateral external fixator.78910 In a study done by Iacobellis et al.,22 no significant differences were observed between the ring fixator and the mono-lateral fixator, but patients tolerated the mono later fixator better. In our study, patients were encouraged to start earlier rehabilitation including ankle joint motion on the second postoperative day. No loss of ankle joint motion and equinus deformity were observed in our cases series. All patients are satisfied with the final results both mentally and physically (SF-36 results). We thus prefer the mono-lateral external fixator over a ring type of external fixator in doing limb lengthening.