Femoral Nerve Palsy in Pavlik Harness Treatment for Developmental Dysplasia of the Hip

Murnaghan, M. Lucas MD, MEd, FRCSC; Browne, Richard H. PhD; Sucato, Daniel J. MD, MS; Birch, John MD, FRCSC

Journal of Bone & Joint Surgery - American Volume:
doi: 10.2106/JBJS.J.01210
Scientific Articles
Abstract

Background: Transient femoral nerve palsy is a potential complication of the use of a Pavlik harness to treat developmental dysplasia of the hip. Our hypothesis was that patients who develop a femoral nerve palsy while undergoing Pavlik harness treatment for developmental dysplasia of the hip are more likely to have unsuccessful orthotic treatment and to require closed or open hip reduction.

Methods: We performed a retrospective review of all patients who underwent Pavlik harness treatment for developmental dysplasia of the hip within a seventeen-year period (1992 to 2008). All cases of femoral nerve palsy were identified and reviewed. Thirty infants met the study criteria and formed the palsy group. A control group of seventy-nine infants who did not develop femoral nerve palsy during treatment was randomly selected.

Results: Thirty cases of femoral nerve palsy were identified from a group of 1218 patients for an incidence of 2.5%. Eighty-seven percent of femoral nerve palsies presented within one week of application of the Pavlik harness. Femoral nerve palsy was more likely in older, larger patients in whom the developmental dysplasia of the hip was of higher severity. Patients whose femoral nerve palsy resolved within three days had a 70% chance of having successful treatment with the Pavlik harness, whereas those who had not recovered by ten days had a 70% chance of having treatment failure with the Pavlik harness. The success rate associated with treatment with a Pavlik harness was 94% in our control group and 47% in our palsy group.

Conclusions: Femoral nerve palsy is an uncommon yet clinically important complication of Pavlik harness treatment for developmental dysplasia of the hip. This complication is strongly predictive of failure of treatment, and its impact is greatest when the developmental dysplasia of the hip is higher in severity. Early recognition and management of femoral nerve palsies may improve the success of treatment.

Level of Evidence: Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

Author Information

1The Hospital for Sick Children, Room S-107 Elm Wing, 555 University Avenue, Toronto, ON M5G 1X8, Canada. E-mail address: lucas.murnaghan@sickkids.ca

2Texas Scottish Rite Hospital for Children, 2222 Welborn Street, Dallas, TX 75219

Article Outline

Arnold Pavlik originally described the use of his harness for the treatment of developmental dysplasia of the hip in 19441. His largest series of 1912 patients brought this dynamic method to the attention of the world2. Further studies have demonstrated consistently high success rates, ranging from 84% to 97%, in the treatment of developmental dysplasia of the hip3-6. In an attempt to better understand the types of patients in whom treatment is not successful, two studies endeavored to define the predictors of failure7,8. Possible complications of Pavlik harness treatment include osteonecrosis of the femoral head, inferior (obturator) dislocation, so-called Pavlik harness disease, brachial plexus palsy, and femoral nerve palsy3,7-12. Although femoral nerve palsy has been recognized and discussed frequently in reports on Pavlik harness treatment of developmental dysplasia of the hip, no study has focused on this complication specifically. Although a variety of theories have been proposed to explain the cause of the femoral nerve palsy, there are no data to support these theories or results4,5,8,9. With each published report including one patient in each of their series, little information is known about the natural history and clinical implications of this entity.

The purpose of this study was to review one center’s experience with femoral nerve palsy occurring during Pavlik harness treatment for developmental dysplasia of the hip. In addition to defining the incidence and potential risk factors for the development of femoral nerve palsy, we sought to correlate this complication with subsequent clinical outcome. Our hypothesis was that patients who develop a femoral nerve palsy while undergoing Pavlik harness treatment for developmental dysplasia of the hip are more likely to have unsuccessful orthotic treatment and to require subsequent closed or open reduction of the hip.

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Materials and Methods

Following approval from our institutional review board, we performed a retrospective review of all patients who underwent Pavlik harness treatment for developmental dysplasia of the hip at our center within a sixteen-year period (1992 to 2008). All cases of femoral nerve palsy were identified and reviewed. Femoral nerve palsy was defined as the infant’s inability to extend the knee either spontaneously or in response to gentle stimulation of the foot. Exclusion criteria included treatment instituted elsewhere, inadequate medical records, or an underlying neuromuscular diagnosis at the time of presentation or during the follow-up period. Thirty patients developed a femoral nerve palsy during harness treatment, and these patients formed our palsy group. A control group of seventy-nine patients was randomly selected from those who did not develop a femoral nerve palsy.

A formal chart review was performed of both the palsy-group subjects and the control-group subjects. The following data were collected: demographics, anthropometrics, clinical history data, Pavlik harness information, physical examination findings, ultrasound results, details of the femoral nerve palsy, and eventual clinical outcome. In addition to the initial consultation and follow-up clinic notes, the chart review was supplemented by nursing records. The nursing record was a prospectively gathered longitudinal record of Pavlik harness treatment, collected by the clinic nurse at the time of initiation of treatment and at the time of all subsequent follow-up visits.

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Statistical Methods

The primary tool was stepwise logistic regression analysis of the probability of a successful Pavlik harness treatment. The variables that significantly correlated with the probability of a successful outcome were then used to estimate that probability. The statistical data analysis for this paper was generated with use of SAS/STAT software, Version 9.1, of the SAS System for Windows (SAS Institute, Cary, North Carolina).

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Source of Funding

This research study was not supported by any external funding.

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Results

Incidence

Thirty (2.5%) of the 1218 patients with developmental dysplasia of the hip who were treated with the Pavlik harness over the period of review were identified as having femoral nerve palsy. All femoral nerve palsies occurred either on the treatment side of a patient with unilateral developmental dysplasia of the hip or on one side of a patient with bilateral developmental dysplasia of the hip. There were no cases in which femoral nerve palsy occurred on the unaffected contralateral side of a patient with unilateral developmental dysplasia of the hip.

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Onset

With respect to the onset of the femoral nerve palsy, eleven of the thirty palsies presented at less than one week, fifteen presented at the one-week follow-up clinic visit, and the remaining four presented at greater than one week. Overall, twenty-six (87%) of the thirty femoral nerve palsies presented at or before the one-week follow-up visit. All femoral nerve palsies that were identified before one week were first noted by the parents and brought to the attention of the treating surgeon. All femoral nerve palsies that were identified at the one-week follow-up visit were identified by the treating surgeon and brought to the attention of the parents. There were no missed appointments at the regularly scheduled one-week visit. In the four palsies noted after one week, all were noted by the treating physician during a regularly scheduled weekly follow-up visit.

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Anthropometrics

The comparison of demographics and anthropometrics between the palsy and control groups is summarized in Table I. On the average, the palsy group patients were older (56 vs. 22 days), taller (55 vs. 51 cm), heavier (4.8 vs. 3.7 kg), and with relatively elevated body-mass index (15.5 vs. 14.3 kg/m2). There was no significant difference in birth weight, bilaterality, sex, or ethnicity. The palsy group patients required larger Pavlik harnesses, on the average, than the control group did. A medium, large, or extra-large harness was required by 35% of patients in the palsy group, but only by 9% of patients in the control group.

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Severity of Developmental Dysplasia of the Hip

The severity of developmental dysplasia of the hip was assessed both clinically and ultrasonographically. We characterized the physical findings in affected hips as follows: dysplasia, Barlow positive13, Ortolani positive14, and fixed dislocation. Figure 1 displays the association between increasing clinical severity of developmental dysplasia of the hip and the presence of femoral nerve palsy. In the control group, 28% of hips had dysplasia, 31% were Barlow positive, 39% were Ortolani positive, and 2% had a fixed dislocation; whereas in the palsy group, 20% of hips had dysplasia, 13% were Barlow positive, 53% were Ortolani positive, and 13% had a fixed dislocation (p = 0.002). The ultrasonographic severity of developmental dysplasia of the hip was characterized with use of the Graf classification system, with all hips in our infants classified as Graf type II (dysplastic), type III (subluxated), or type IV (dislocated)15. Figure 2 displays the association between ultrasonographic severity and the presence of femoral nerve palsy. In the control group, 38% of hips displayed Graf-II severity, 33% displayed Graf-III severity, and 29% displayed Graf-IV severity; whereas in the palsy group, 26% of hips displayed Graf-II severity, 4% displayed Graf-III severity, and 70% displayed Graf-IV severity (p = 0.0004).

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Outcome: Pavlik Success

The success rate of Pavlik harness treatment in our control group was 94%. The success rate for the patients who developed a femoral nerve palsy (the palsy group) was 47% (p < 0.0001). There was a difference between the two groups with respect to successful Pavlik harness treatment and the severity of developmental dysplasia (Fig. 3). In the control group, the success rate of Pavlik harness treatment was as follows: 99% for hips with dysplasia, 98% for hips that were Barlow positive, 83% for hips that were Ortolani positive, and 58% for hips with fixed dislocation; in the palsy group, the success rate was 86% for hips with dysplasia, 84% for hips that were Barlow positive, 31% for hips that were Ortolani positive, and 10% for hips with fixed dislocation.

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Return of Function

All patients had return of femoral nerve function; however, there was substantial variability in the speed of return (Fig. 4). Patients in whom Pavlik harness treatment was successful had return of femoral nerve function at an average of five days. Patients in whom Pavlik harness treatment was not successful had return of femoral nerve function at an average of fifteen days. According to the stepwise logistic regression analysis, the number of days until return of femoral nerve function was predictive of the probability of success with Pavlik harness treatment. Table II demonstrates how an increase in the number of days until return of femoral nerve function correlated with a decrease in the probability of successful treatment with the Pavlik harness. Patients whose femoral nerve palsy resolved in three days had a 70% chance of successful treatment with the Pavlik harness. In contrast, patients whose femoral nerve palsy had not resolved by ten days had almost a 70% chance of unsuccessful treatment with the Pavlik harness.

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Other Data

There was variability in how the femoral nerve palsies were managed by the treating surgeon, with eight different surgeons involved in the treatment of developmental dysplasia of the hip during this time period. Nineteen patients with femoral nerve palsy were treated with temporary suspension of harness treatment and subsequent reapplication when femoral nerve function returned. Six were treated with adjustment of the Pavlik harness to reduce hip flexion. Five were managed with complete abandonment of the harness, with four requiring subsequent closed or open reduction of the hip. There was no correlation between the method of management of the femoral nerve palsy and the success of treatment. Of those patients who did have reinstitution of harness therapy, only three developed a recurrence of the palsy. Pavlik harness treatment was abandoned in all patients who demonstrated recurrence of femoral nerve palsy. All patients had eventual complete return of full quadriceps function, with no clinically evident long-term motor or sensory deficit. There were no cases of permanent femoral nerve palsy.

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Discussion

Femoral nerve palsy has been identified in the literature as a possible complication of Pavlik harness treatment and is highlighted in the classic article by Ramsey et al.5. They noted a single case of femoral nerve palsy in a single patient outside of their study group and hypothesized that the palsy developed from forced flexion and possible entrapment of the femoral nerve under the inguinal ligament. Kalamchi and MacFarlane described a single patient with a transient nerve palsy that resolved spontaneously within two weeks after the patient’s harness had been adjusted to maintain reduced flexion of the hips4. They recommended careful assessment of quadriceps function at each visit and avoiding flexion of >90°. Specific mention was made of caution in the “obese child.” Mubarak et al. specified the recommendations by stating that hip flexion of >120° should be maintained only for the two to three-week trial of spontaneous reduction and then reduced to 90° to 100°9.

Our study identifies new information pertaining to the development of femoral nerve palsy during Pavlik harness treatment of developmental dysplasia of the hip. The overall prevalence of femoral nerve palsy in our study was 2.5%. This information is important in counseling parents as well as providing guidelines for monitoring treatment with the Pavlik harness. The diagnosis of femoral nerve palsy was made in the first week of Pavlik harness treatment in 87% of patients. Less than half of these palsies were first noticed by the parents, and 58% were only diagnosed at the time of the first follow-up by the physician. This discrepancy must be understood when considering telephone follow-up and parent-reported concerns. The hypothesis that larger patients are at increased risk of femoral nerve palsy is supported by the findings of our study. Although the protocol at our center was to place the hip in at least 90° of flexion, the specific degree of flexion was not adequately documented in the medical record to allow any correlation between actual degree of flexion and the development of femoral nerve palsy.

One striking finding of this study was the impact of femoral nerve palsy on the need to proceed to open or closed reduction of the affected hips. The overall success of Pavlik harness treatment was 94% in the control group as compared with 47% in the palsy group. The impact of femoral nerve palsy was greatest on hips that were either Ortolani positive (83% success in the control group vs. 31% in the palsy group) or had a fixed dislocation (58% in the control group vs. 10% in the palsy group). It appears that the frankly dislocated hip is most affected by the abandonment (temporary or permanent) of the Pavlik harness, whereas the simply dysplastic or dislocatable hip can tolerate a brief interruption in harness treatment.

There was a clear association between the number of days that the femoral nerve palsy persisted and the probability of success of Pavlik harness treatment. If the femoral nerve palsy persisted beyond three days, the probability of success was only 30% in our study population. This finding encourages the treating physician to recognize femoral nerve palsies early and reinstitute treatment quickly following resolution of the palsy. We recommend that the harness should only be adjusted or temporarily suspended and not completely abandoned and that the follow-up before resuming standard positioning should be minimized to a few days instead of a full week or more.

The present study has a number of limitations that should be emphasized. First, although all data were collected prospectively with use of a clinical data collection form, the extraction and analysis of these data were performed in a retrospective manner. Second, this study represents one center’s experience and may not represent the experience of other centers or centers that used a different treatment protocol. The institution in which this study was carried out serves as a referral center for a large population with a broad geographic distribution. As the patients were treated over a sixteen-year period by eight different attending orthopaedic surgeons, there was variability in the management of the femoral nerve palsies. Third, the control group was created by a representative sample of the entire non-palsy population and may not reflect that group precisely.

In conclusion, femoral nerve palsy is an uncommon yet clinically important complication of Pavlik harness treatment. It is strongly predictive of failure of treatment, and its impact is greatest in patients who have an increased severity of developmental dysplasia of the hip. The identification of femoral nerve palsy should prepare the parents as well as the treating surgeon for the increased likelihood of the need for closed or open hip reduction. Early recognition and management of femoral nerve palsies should improve the success rate associated with treatment of developmental dysplasia of the hip.

NOTE: The authors thank Paul Jamieson (University College Dublin) for his help in preparation of the manuscript.

Investigation performed at Texas Scottish Rite Hospital for Children, Dallas, Texas

Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.

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