Familial Hypophosphatasia

Case: Hypophosphatasia

Reported by Myles Clough, Orthopaedic Surgeon, Kamloops, BC, Canada

72 year old female presented for review with right hip pain. She is nearly wheelchair bound. She has progressive shepherd's crook deformity of the right hip with cutting out of the previously central internal fixation.

She had previously presented at age 55 with an intertrochanteric R hip fracture which went on non-union. This was unusual enough for us to investigate her for metabolic bone disease. She was found to have a familial form of hypophosphatasia. She had bilateral Zickel nail fixation of her proximal femurs. Subsequently she had a fracture at the nail tip on the left and was revised in 1991 to a gamma nail (elsewhere).

Now she presents with hip pain, shepherds crook deformity of the proximal right femur and the nail has cut out of the trochanteric region and perhaps out of the femoral head. Her sister who likely had the same condition had three unsuccessful total hip replacements with early loosening. The sister eventually died with the problem unresolved after a fall and head injury. My patient is terrified of having a hip replacement.

Right hip Xray, 1998

Right hip Xray, 2000

AP pelvis Xray, 2000

If this was a simple situation I would offer her sub-trochanteric osteotomy to realign the femoral neck, then fixation with a plate. Unfortunately neither she nor I have any confidence she will heal after that unless the fixation is total bone contact (i.e. intramedullary). So I am considering subtrochanteric (dome) osteotomy and exchange nailing. She has seen metabolic bone disease experts as recently as a year ago with no suggestions as to covering the surgical situtation with any medical treatment.

Questions

1. What do you think of the surgical plan? Any other suggestions?
2. Would it be a good idea to infuse pamidronate pre and post op?
3. Any tips or experience with adult hypophosphatasia?

Detailed History

This patient initially presented at age 55 with a subtrochanteric fracture of the right hip. Past medical history included fractures of both patellae, both of which went on to patellectomies. She was treated surgically using a (Richards) sliding nail plate on Feb 27 1983. She went on apparently to heal and was followed until May 1983 after which she was lost to follow up.

In October 1983 she re-presented with an apparent wound infection. An abscess was drained although no organism was cultured. Tomograms showed a persistent lucent line at the fracture site. However, at surgery to revise the plate the fracture appeared healed. The infection settled after the plate was removed.

In Jan 1984 she described left thigh pains and xrays of this area showed a stress fracture (Looser zone). She was reviewed by the Metabolic Bone Disease unit and a diagnosis of hypophosphatasia was made.

The investigations during the Feb 1984 admission to the Metabolic Bone Disease Unit were as follows:

Details of the case were sent to Dr.M.P.Whyte a recognised authority on the subject of hypophosphatasia. His reply read, in part, "it is my impression that rodding procedures to correct pseudo fractures are more effective than plating". Our impression at this stage (May 1984) was that the right side had healed but that both sides had Looser zones.

The patient did not agree to a prophylactic rodding of the left femur but presented in June 1984 with a sudden increase in right sided thigh pain and evidence on Xray of non-union and angulation of the fracture. She underwent Zickel nail fixation of the right femur on August 16th 1984. As the nail was passed it caused fracturing of the proximal part of the femur. However fixation into the femoral head was satisfactory. There was no evidence of infection and good post operative pain relief.

At 2 months post operation there was continued pain relief but no signs of healing. At 5 months post operation she was only experiencing pain from the nail head protruding into the buttock. Xrays showed signs of healing. The zone on the left side had extended and she was extremely painful in this thigh.

She underwent Zickel Nail fixation of the left femur May 7 1985. She was followed up to November 1985 with healing of both sides noted. She continued to have discomfort from the prominent nail in the right buttock.

In 1991 following a fall she had a fracture of the left femur at the tip of the nail (distally). This was treated (elsewhere) by exchange of the nail for a Gamma nail with distal locking below the fracture. She went on to heal this.

In August 1998 she presented again with pain in the right hip. The Xray showed shepherd's crook (varus) deformity of the right hip with the nail in danger of cutting out into the right femoral head. The right leg was noted to be 1 cm shorter. She had walked without a cane until May 1998.

I asked for further review from the Metabolic Bone Disease specialist. This did not take place until September 1999. Findings then were as follows:

She did not follow up with me until December 2000. She is now dependent on a walker and has pain with any movement of the right hip. She has been booked for exchange of the Zickel Nail for a Recon Nail with subtrochanteric osteotomy.

Bibliography

Premature exfoliation of teeth in childhood and adolescence. (Review) Advances in Pediatrics 1994;41:453-70

OMIM Database

The Magic Foundation (Chicago, Illinois, USA)

Bone dysplasias South Australian Orthopaedic Registrars' Notebook

MIR Teaching case bs070 http://gamma.wustl.edu/bs070te145.html