Limb lengthening with a fully implantable mechanical distraction intramedullary nail

AIM: The morbidity of fixator-assisted distraction osteogenesis should be reduced by intramedullary lengthening devices. The ISKD (intramedullary skeletal kinetic distractor) is a new, fully implantable mechanical lengthening nail. In a prospective cohort trial the possibilities and limitations of the device used on femur and tibia are examined. METHODS: 22 patients with a mean age of 25 (range: 16-46) years were treated with an ISKD for femoral (n = 16) and tibial (n = 6) lengthening. The average leg length discrepancy was 48 (range: 25-80) mm. The follow-up was 21 (range: 7-37) months. Clinical and radiological results and complications were evaluated. RESULTS: The results of femoral and tibial applications of the ISKD are different. At the tibia, in three patients a pseudarthrosis occurred and slow callus formation was observed twice. An equinus contracture became evident in 2 patients. At the femur, in one case the lengthening was not accomplished with the device. Five patients were manipulated under anaesthesia at least once to achieve the aim of distraction. Three of these patients received retrograde implantation of the ISKD. An infection or interlocking screw failure was not observed either at the femur or the tibia. CONCLUSION: The ISKD reduces fixator-associated problems but incorporates its own difficulties which are mainly based on the guidance of the device. Careful patient advice in monitoring the lengthening process is mandatory. At the femur 8 cm of lengthening can be achieved but the nail tends to "block". Proper reaming and osteotomy techniques are important. A lengthening of more than 1 mm/day is recommended to prevent early consolidation. At the tibia weak callus formation and soft tissue contractures occur, therefore not more than 4 cm lengthening should be planned, the distraction speed has to be reduced noticeable below 1 mm/day and the initial immobilisation should be for more than a week.     

Limb lengthening by epiphyseal distraction. An experimental study in the caprine femur

Epiphyseal distraction of the left distal femur was accomplished in 10 goats (aged 3-4.5 months). A modified Hoffmann external fixation device was used as a unilateral distraction frame. A distraction rate of 1.5 mm/day was applied for 5.5 weeks. Epiphysiolysis occurred after 3-7 days of distraction. After the lengthening procedure, the growth plate had reduced in height in eight animals on radiographic examination. In two animals the growth plate was fused. Three animals were killed at 4 (Group 1) and 8 (Group 2) weeks and four animals at 16 (Group 3) weeks after the end of the distraction period. The gain in leg length obtained by distraction was reduced owing to growth retardation in the distal femur of the operated limb. The average final lengthening was 24.9, 19.4, and 13.4% in Groups 1, 2, and 3, respectively. Femur and tibia from both sides were tested mechanically in torsion. Only one femur fractured in the elongation area. All but one elongated femur fractured in the area of the diaphysis subjected to distractional force. The torsional strength of the elongated femur compared with control was reduced to approximately 50% in all groups. The corresponding torsional strength of the tibia on the elongated extremity compared with control was reduced to approximately 75% in all groups. The difference in relative strength of femur compared with that of tibia was statistically significant. This finding can be explained by a stress-protective effect on the femur in the distraction area caused by the external device.     

Biomechanical investigation of distraction forces appearing in the course of femoral lengthening in rabbits: radiological and histological study]

This study was conducted in order to determine the values of forces necessary to stretch bony fragments during tibia lengthening in rabbits. The aim of this study was to determine the conditions which lead to complications of the lengthening process related to the rate of distraction. The experiment was conducted on 16 rabbits of New Zealand breed. The construction of the apparatus eliminated tension resulting from the so-called "bending moment". In all rabbits distraction was began on the 5th day after fixing the apparatus. The standard rate of lengthening was 2 x 0.25 mm per day. In 8 rabbits the rate of distraction was regulated. The distraction forces were measured and electronically recorded during the distraction procedure, during the animal's movement and resting position at strictly monitored intervals. Radiological examination of the lengthened tibia was performed once a week. Histological examination was performed in three rabbits after completion of the experiment. We made 328 measurements of the involved distractive forces, collecting a total of 223 MB of data. Graphical representation of the lengthening force and it's performance turned out to be similar for various experimental animals and it's course was typical for every stage of the lengthening process. At the time of distraction of the apparatus the measured force increased on average by 0.87 N (minimum 0.61, maximum 1.1N). Abnormal rates of distraction resulted in a break of the callus continuity in 3 rabbits. Radiological and histological examinations were used to assess to confirm certain observations concerning the technique and rate of distraction.     

Clinical application of the tension-stress effect for limb lengthening

For 40 years, the author has been developing a system of orthopedics, traumatology, and limb lengthening using a circular transfixion-wire external skeletal fixator, often in combination with biomechanic methods of stimulating the formation of new osseous tissue within a widening osteotomy distraction site. The factors important for neoosteogenesis after osteotomy include: maximum preservation of extraosseous and medullary blood supply; stable external fixation; a delay prior to distraction; a distraction rate of 1 mm per day in frequent small steps; a period of stable neutral fixation after lengthening; and physiologic use of the elongating limb. For a successful fixator application, the apparatus must be applied with consideration given to the number, size, and location of the rings, the placement and tension on the wires, the technique of wire insertion, the effect of soft-tissue transfixion on limb use, and the prevention of bone and joint deformities caused by countertension in soft tissues. Clinical application of the author's techniques permits stature increase in certain forms of dwarfism, correction of deformities and limb-length inequalities, and stump elongation. For many of these applications, motorized distraction can provide continuous limb lengthening while the apparatus is on the patient.     

Verlängerung der unteren Extremität mit dem Intramedullary Skeletal Kinetic Distractor (ISKD)

OBJECTIVE: Callus distraction of the femur or tibia with an intramedullary distractor, which lengthens mechanically through alternating rotations of at least 3 degrees. INDICATIONS: Femoral or tibial shortening between 20 and 80 mm. Angular and rotational deformities can be corrected at the osteotomy site. CONTRAINDICATIONS: Open epiphyses. Small medullary canal (after intramedullary reaming femoral diameter < 14.5 mm, tibial diameter < 12.5 mm). Severe deformities. Insufficient compliance. Osteitis. Soft-tissue infections. SURGICAL TECHNIQUE: Supine position. Femoral shaft osteotomy at the proximal or middle third by multiple drill holes completed with a chisel. For lengthening of the tibia, osteotomy with a Gigli saw is preferred. Control of the rotation by two parallel 3.0-mm Kirschner wires. Correction of angular or rotational deformities. Via stab incision reaming of the medullary canal with a flexible reamer. The femur is overreamed 2.0 mm and the tibia 1.5 mm above the desired implant diameter. Insertion of the Intramedullary Skeletal Kinetic Distractor (ISKD) into the medullary canal and distal locking in freehand technique. Control of the rotation and of the osteotomy gap. Proximal locking with an aiming device. For femoral lengthening 3 days and for tibial lengthening 5 days postoperatively the distraction is begun by increasing mobilization with partial weight bearing, to achieve daily distraction of 1 mm. In case of insufficient distraction, additional rotations are performed by the patient while checking the external monitor that displays the daily and total distraction length. RESULTS: Intramedullary lengthening with the ISKD was performed in four patients having an average age of 29 years (18-36 years). Two femoral shortenings were combined with complex rotational and angular deformities. The average lengthening of three femora and one tibia was 31 mm (26-40 mm). The average intraoperative blood loss was 230 ml (110-320 ml), the mean surgical time 108 min (90-145 min). The average daily distraction amounted to 1.2 mm (0.9-1.8 mm). Full weight bearing was permitted after 10 weeks (7-14 weeks), return to regular work after 11 weeks (7-16 weeks). At follow-up examination of an average of 2.3 years postoperatively the knee range of motion was full. Consolidation was noted 80 days (51-111 days) postoperatively with an average consolidation index of 2.9 days/mm (1.8-4.1 days/mm). No complications were observed. According to the Paley Score all patients had an excellent outcome.     

First experience with correction of limb-length inequality and angular and rotational deformities of the tibia using the Taylor spatial frame

The authors analyse the first results of correction surgery for limb-length inequality and rotational and angular deformities of the tibia using the Taylor spatial frame in combination with the Ilizarov external fixator in three patients. The shortening of the tibia, 65 mm on the average (55, 60 and 80 mm, respectively), was due to tibial hemimilia in two patients and traumatic epiphyseolysis of the distal tibia in one patient. Distraction at a rate of 1 mm/day was controlled three-times a day on two contralateral struts. It started on the seventh day after osteotomy in all three patients. On the second post-operative day, rehabilitation started with standing up and walking with crutches. The additional fixation of the heel and foot was removed at 3 months after distraction was terminated so that ankle exercise would be possible. No serious complications were recorded. The average distraction index was 0.91 and the average tibial lengthening was 65 mm. Callus consolidation was achieved at 131 days after the end of distraction phase. Approximately at 10 months post-operatively, the patients reported full weight-bearing of the extremity.     

Lower extremity lengthening by Wagner's method and by callus distraction

Fifty-three patients underwent 64 lengthenings of the femur or tibia by the Wagner technique or by the callus distraction method. Thirty-six femoral and 28 tibial segments were lengthened. Simultaneous lengthening of the femur and tibia was performed in seven limbs. Three segments underwent repeat lengthenings. The average length gained by the Wagner method was 5.1 cm in the femur and 5.4 cm in the tibia. Length gains by callus distraction were 4.9 cm in the femur and 4.5 cm in the tibia. Complication rates were fewer and less severe with callus distraction. The number of operations, days of hospitalization, and length of total treatment were less in patients operated on with the callus distraction method than in those who underwent the Wagner technique.     

Lower limb lengthening by a modified Wagner technique

A series of 50 patients who underwent femoral and tibial lengthenings using the Wagner apparatus is reviewed. Satisfactory gains in leg length with an acceptably low complication rate were achieved. Both substitution of cortical osteotomy for complete osteotomy and delaying of distraction increased callus formation. The particular problems of lengthening the congenital short femur and tibia are discussed.     

Injury and regeneration of intramuscular connective tissue subjected to various regimes of distraction

Objective： To investigate the effect on intramuscular connective tissue and passive range of joint motion by the stress produced in limb lengthening.
Methods： An animal model of limb lengthening was established in the tibia of rabbits. Distraction was initiated at a rate of 1 mm/d and 2 mm/d in two steps respectively, and both proceeded until 10% and 20% of the tibia length was achieved. Muscle samples were harvested at the time when distraction ended and at the 4th week of consolidation after the distraction. Scanning electron microscope was applied to observe the morphological changes of the perimysium. The goniometer, which we made for this study, was used to measure the passive range of joint motion.
Results： The collagen fibers were partitioned in bundles, crimped and interconnected closely and orderly. In the regime of 1 mm/d distraction with 10% lengthening, no apparent changes of the collagen fiber and passive range of joint motion was demonstrated. When tibia was increased to 20%, the crimped fibers showed a tendency of being straightened while the passive range of joint motion was reduced. The findings remained the same at the 4th week ofconsolidation. In the regime of 2 mm/d distraction with 10% lengthening, the crimped structure of the collagen fibers in the perimysium disappeared and the fibers were almost straightened. Additionally, the interconnection of the collagen fibers became loosened and interstice was presented among the fibers. At the 4th week of consolidation, the restoration to the original crimped structure was not completed. When the lengthening ratio was increased to 20%, the collagen fibers were straightened completely. This condition remained unchanged throughout all 4 weeks. The passive range of joint motion was reduced dramatically in the regime of 2 mm/d distraction.
Conclusion： The ultrastructure of perimysium and the passive range of joint motion in the regime of lmm/d lengthening shows the condition closest to the normal ones. The regime of 2 mm/d lengthenin     

Limb lengthening and correction of deformity in the lower limbs of children with osteogenesis imperfecta

We performed limb lengthening and correction of deformity of nine long bones of the lower limb in six children (mean age, 14.7 years) with osteogenesis imperfecta (OI). All had femoral lengthening and three also had ipsilateral tibial lengthening. Angular deformities were corrected simultaneously. Five limb segments were treated using a monolateral external fixator and four with the Ilizarov frame. In three children, lengthening was done over previously inserted femoral intramedullary rods. The mean lengthening achieved was 6.26 cm (mean healing index, 33.25 days/cm). Significant complications included one deep infection, one fracture of the femur and one anterior angulation deformity of the tibia. The abnormal bone of OI tolerated the external fixators throughout the period of lengthening without any episodes of migration of wires or pins through the soft bone. The regenerate bone formed within the time which is normally expected in limb-lengthening procedures performed for other conditions. We conclude that despite the abnormal bone characteristics, distraction osteogenesis to correct limb-length discrepancy and angular deformity can be performed safely in children with OI.     

Callus formation in the humerus compared with the femur and tibia during limb lengthening

We investigated whether the callus formation in the humerus during the distraction period of limb lengthening proceeds at a higher rate than that in the femur and tibia. Ten achondroplastic patients underwent 3 bilateral humerus, 3 bilateral femur and 4 bilateral tibia lengthenings. To reduce the confounding effect of bone size, we used bone mineral apparent density (BMAD) to compare the three groups; this is a volumetric bone mineral density measurement. BMAD in the distracted callus space was evaluated at 8 weeks after the start of distraction using dual-energy X-ray absorptiometry (mean ± SD; g/cm³): in the humerus (0.24 ± 0.08) it was significantly higher than in the tibia (0.10 ± 0.02), while there was no difference between the humerus and femur (0.35 ± 0.11). We conclude that the callus formation in the humerus during the distraction period of limb lengthening proceeded at a significantly faster rate than in the tibia, but there was no significant difference between the humerus and femur. Received: 4 March 1997     

Growth disturbance after lengthening of the lower limb and quantitative assessment of physeal closure in skeletally immature patients with achondroplasia

This study evaluated the effect of limb lengthening on longitudinal growth in patients with achondroplasia. Growth of the lower extremity was assessed retrospectively by serial radiographs in 35 skeletally immature patients with achondroplasia who underwent bilateral limb lengthening (Group 1), and in 12 skeletally immature patients with achondroplasia who did not (Group 2). In Group 1, 23 patients underwent only tibial lengthening (Group 1a) and 12 patients underwent tibial and femoral lengthening sequentially (Group 1b). The mean lengthening in the tibia was 9.2 cm (59.5%) in Group 1a, and 9.0 cm (58.2%) in the tibia and 10.2 cm (54.3%) in the femur in Group 1b. The mean follow-up was 9.3 years (8.6 to 10.3). The final mean total length of lower extremity in Group 1a was 526.6 mm (501.3?to 552.9) at the time of skeletal maturity and 610.1 mm (577.6 to 638.6) in Group 1b, compared with 457.0 mm (411.7 to 502.3) in Group 2. However, the mean actual length, representing the length solely grown from the physis without the length of distraction, showed that there was a significant disturbance of growth after limb lengthening. In Group 1a, a mean decrease of 22.4 mm (21.3 to 23.1) (4.9%) was observed in the actual limb length when compared with Group 2, and a greater mean decrease of 38.9 mm (37.2 to 40.8) (8.5%) was observed in Group 1b when compared with Group 2 at skeletal maturity. In Group 1, the mean actual limb length was 16.5 mm (15.8 to 17.2) (3.6%) shorter in Group 1b when compared with Group 1a at the time of skeletal maturity. Premature physeal closure was seen mostly in the proximal tibia and the distal femur with relative preservation of proximal femur and distal tibia. We suggest that significant disturbance of growth can occur after extensive limb lengthening in patients with achondroplasia, and therefore, this should be included in pre-operative counselling of these patients and their parents.     

Femur lengthening with a telescopic intramedullary nail ISKD--method presentation and early clinical results

INTRODUCTION: Limb discrepancy over 4 cm is an indication for limb lengthening. Surgical techniques rely on osteotomy, external stabilisation and gradual distraction. The ISKD (Intramedullary Skeletal Kinetic Distractor) nail allows distraction osteogenesis and no external fixator is required. AIM OF PAPER: Aims of paper are: presentation of limb elongation method with the ISKD device, and presentation of early own results. MATERIAL AND METHODS: Material consists of 5 patients, age 14-16 years, 3 boys and 2 girls, who underwent femur lengthening with the ISKD nail between 2005 and 2007. We evaluated: initial shortening, surgical procedure, complications, amount of lengthening, lengthening rate, distraction index, time of treatment and mobility of adjacent joints. RESULTS: Initial shortening was 4-11 cm. No surgical complications were observed, mean time of surgery was 145 minutes, mean blood loss--200 ml. In three patients difficulties with initial distraction required manipulations under general anaesthesia. Distraction was complicated in 3 cases--in two patients premature consolidation was noted; in one case the distraction rate was too high. Mean lengthening rate in the study group was 0.7 mm/day (0.6-0.7 mm/day). Mean distraction index was 41.7 days/cm (26.2-55 days/cm). Full weight bearing was allowed after mean 234 days (210-275 days). Transient decrease of adjacent joint mobility was observed. CONCLUSION: The fully implantable, telescopic ISKD eliminates the need of external fixation and associated complications. Early results of limb lengthening with ISKD are encouraging. Careful patient selection and preoperative planning is required. Further studies and longer follow-up periods are needed.     

Längenkorrekturen der unteren Extremität mit voll implantierbaren Distraktionsmarknägeln

All commercially available fully implantable intramedullary distraction nails, Albizzia®, Fitbone® II and ISKD, were used for lengthening of the femur and tibia. Albizzia® has the best cost-performance ratio: the lengthening capacity is 100 mm; the stability tolerates early weight bearing and unlimited physiotherapy immediately after the operation; it has a reliable feed with safe function and so requires only a few clinical and radiological controls. The first activation of the lengthening system needs careful guidance by the surgeon. Fitbone® II appears easy to handle without active cooperation of the patient, and at present it is the only nail for simultaneous lengthening of four regions. It is expensive with limited stability and control and requires frequent clinical, sonographic and radiological controls. It allows the shortest maximal lengthening. ISKD is priced between Albizzia® und Fitbone® II, does not allow early weight bearing, is difficult to control and cannot be used for simultaneous lengthening. Internal systems for callus distraction are superior to the external devices in many respects: shorter hospitalization and rehabilitation times, low infection risk, more extensive physiotherapy, better aesthetic outcome and minimal consequential costs.     

Comparison between upper and lower limb lengthening in patients with achondroplasia: a retrospective study

Lengthening of the humerus is now an established technique. We compared the complications of humeral lengthening with those of femoral lengthening and investigated whether or not the callus formation in the humerus proceeds at a higher rate than that in the femur. A total of 24 humeral and 24 femoral lengthenings were performed on 12 patients with achondroplasia. We measured the pixel value ratio (PVR) of the lengthened area on radiographs and each radiograph was analysed for the shape, type and density of the callus. The quality of life (QOL) of the patients after humeral lengthening was compared with that prior to surgery. The complication rate per segment of humerus and femur was 0.87% and 1.37%, respectively. In the humerus the PVR was significantly higher than that of the femur. Lower limbs were associated with an increased incidence of concave, lateral and central callus shapes. Humeral lengthening had a lower complication rate than lower-limb lengthening, and QOL increased significantly after humeral lengthening. Callus formation in the humerus during the distraction period proceeded at a significantly higher rate than that in the femur. These findings indicate that humeral lengthening has an important role in the management of patients with achondroplasia.     

Leg lengthening by distraction osteogenesis using the Ilizarov apparatus: a novel concept of tibia callus subsidence and its influencing factors

This article studies the incidence and magnitude of delayed callus subsidence, which will also help in study the hypothesis of three cortex corticalisation to determine the time of fixator removal during distraction osteogenesis (DO). Eighty-one tibia segments with mean lengthening of 7.7 ± 2.9 cm were studied with age, gender, skeletal maturity, amount and percentage of lengthening, callus pattern, callus shape, number of cortices seen at the time of fixator removal, bone mineral density (BMD) ratio, and callus diameter ratio analysed for their effect on callus subsidence. All segments had tibia callus subsidence ranging from 4 mm to 3.2 cm with 54% having significant subsidence of more than 1 cm. Multivariate regression analysis revealed only the amount of lengthening and callus patterns to be significant. In conclusion, we can say that tibia callus subsidence is a significant delayed complication and factors affecting it can be used to determine the time of fixator removal.     

Growth retardation after experimental limb lengthening by epiphyseal distraction

Growth retardation occurring as a result of limb lengthening by epiphyseal distraction in two animal species was quantified by using femur or tibia as the experimental bone. The growth plate subjected to distraction appeared radiolucent after the lengthening procedure but was less distinct and had reduced height as compared with the control. In seven of 22 animals, the growth plate of the lengthened bone appeared to close earlier than in the control. After lengthening, bilateral longitudinal growth was evaluated semiquantitatively from radiographs until growth had ceased or residual growth was negligible. Growth retardation was consistently experienced in all animals, with an average reduction in growth potential of each study ranging from 40 to 70%. The results show that epiphyseal distraction is a valid method of limb lengthening, but it appears to have a consistently harmful effect on the growth plate and should be used clinically only in patients close to maturity.     

Effect of rhythm and level of distraction on muscle structure: an animal study

To determine the optimal rhythm of distraction and level of osteotomy for maximal muscle preservation during limb lengthening, histologic and ultrastructural analysis of the peroneus tertius muscle was performed in 46 goats. Thirty-nine animals with 20% or 30% tibial lengthening at the rate of 0.75 mm per day at each osteotomy level were divided in two groups. The first group included 15 animals undergoing tibial middiaphyseal lengthening with automated distractor producing one (n = 5), four (n = 5), or 720 (n = 5) increments per day. The second group included 24 animals in which lengthening was performed at the proximal (n = 4), middle (n = 6), distal (n = 6), or double (n = 8) level of the tibia with distraction rhythm of three times per day. The remaining seven animals served as controls. Histomorphologic features of the lengthened muscles were characterized by a polymorphous appearance with foci of necrosis, atrophy, and sclerosis scattered among apparently normal muscle fibers. The intensity and dispersion of degenerative changes were in direct proportion to the amount of lengthening but in reverse proportion to the frequency of distraction. Tibial lengthening at the diaphysis caused intense fibroblast proliferation and remarkable muscle sclerosis, whereas metaphyseal distraction was associated with a predominance of muscle tissue regeneration over atrophy and sclerosis. Bifocal lengthening and a more fractionated rhythm of distraction were associated with enhanced preservation of existing muscle fibers and greater regenerative activity of the muscle.     

The deep fascia in response to leg lengthening with particular reference to the tension-stress principle

OBJECTIVE: To investigate the morphological changes of deep fascia subjected to distraction in a rabbit model of leg lengthening. METHODS: The animal model of leg lengthening was established in 20 New Zealand white rabbits using a unilateral external fixator with 4 half pins medially fixed to the tibia, and osteotomy was performed between the second and the third pins. The distraction was initiated 7 days after the osteotomy procedure, with the rate of 1 and 2 mm/d in 2 steps, and proceeded until 10% and 20% increases in the initial length of the tibia had been achieved. The deep fascia samples were studied by the hematoxylin-eosin stain, the Masson-trichome staining, and the JEM2000EX electron microscopy. RESULTS: Under light, the cross section of normal deep fascia without distraction consisted of 3 layers. Whereas in the longitudinal sections, the deep fascia consisted of wavy collagen fibers. The normal deep fascia consisted of fibrocyte and collagenous fibrils under electron microscopy. After leg lengthening, the morphology of the fascia distracted at each rate changed. Under light, the fascia distracted at each rate kept the normal 3 layers in the cross sections. The fascia subjected to distraction at a rate of 2 mm/d showed injuries of collagen fibers. Under electron microscopy, the fascia distracted at a rate of 2 mm/d showed active metabolism to repair the necrotic collagenous fibrils. Whereas the fascia subjected to distraction at a rate of 1 mm/d showed regenerative changes. The endotheliocyte of capillaries within the deep fascia subjected to distraction at a rate of 1mm/d with 20% lengthening of tibia was metabolically active. CONCLUSIONS: The tension stress, which is applied in leg lengthening and deformity correction as described by Ilizarov, has a great effect upon the fascia, which is always related to the function of the involved limb. The appropriate regimen of distraction at the rate of 1 mm/d with 20% lengthening of tibia leads to the regenerative changes in deep fascia, ultimately close to the morphological structure of normal under the condition of this investigation.     

Accurate limb-length equalization during total hip arthroplasty

A method of equalization of limb lengths during total hip arthroplasty (THA) was developed that uses the concept of precise reproduction of the position of the femur in space (abduction/adduction) by use of a carpenter's level. Precise reproduction of the femoral position allows accurate measurement of the distance between the pelvis and femur before hip dislocation and after trial component placement allowing accurate measurement of the change in the distance between the femur and pelvis. Accordingly, limb length can be maintained or adjusted to match the contralateral side with increased accuracy. A prospective study was performed with 117 consecutive patients undergoing THA to assess the accuracy of an intraoperative limb-length measuring device. Patients were sequentially randomized into two groups. Group A patients underwent THA without the use of the measuring device, and group B underwent THA using the device. Radiographic assessments of limb lengths were measured using the method of Williamson and Reckling. The hips in group B had a statistically significant decrease in limb-length inequality after THA compared with group A (P<.01). Average postoperative limb-length inequality was 8.8 mm and 3.4 mm for groups A and B, respectively. Three (5%) of 58 group B patients and 18 (31%) of 59 group A patients had a radiographic postoperative limb-length inequality >12 mm (P<.01). Eighty-four of group B patients had limb lengths within 6 mm of the contralateral side compared with 30% of group A patients. Twenty-four percent of group A patients and 7% of group B patients had a symptomatic limb-length inequality that required a heel lift (P<.01).