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Letters to the Editor to:

Scientific Articles:
Patrick Tropiano, Russel C. Huang, Federico P. Girardi, Frank P. Cammisa, Jr., and Thierry Marnay
Lumbar Total Disc Replacement. Seven to Eleven-Year Follow-Up
J Bone Joint Surg Am 2005; 87: 490-496 [Abstract] [Full text] [PDF]
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Electronic letters published:

[Read Letter to the Editor] Dr Huang and Colleagues respond to Dr. Theruvil, et al
Russel C. Huang, Patrick Tropiano, Federico P. Girardi, Frank P. Cammisa, Jr., Thierry Marnay   (21 April 2005)
[Read Letter to the Editor] Lumbar Total Disc Replacement
Bipin Theruvil, FRCS, Praveen Mundlur, Chris Dare, Elias Rahall   (20 April 2005)

Dr Huang and Colleagues respond to Dr. Theruvil, et al 21 April 2005
Previous Letter to the Editor Top
Russel C. Huang,
Assistant attending orthopaedic surgeon
Hospital for Special Surgery,
Patrick Tropiano, Federico P. Girardi, Frank P. Cammisa, Jr., Thierry Marnay

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Re: Dr Huang and Colleagues respond to Dr. Theruvil, et al

huangr{at}hss.edu Russel C. Huang, et al.

To the Editor:

We thank Dr.Mundlur and colleagues for their interest in our article. It does indeed appear that maintenance of segmental motion is critical to prevent adjacent segment degeneration (ASD). The radiographic outcomes of the patients in our study were reported separately[1]. The mean prosthetic flexion- extension range of motion (ROM) was 3.8 degrees at mean 8.7 years. The incidence of radiographic (not symptomatic) ASD was 24%. Mean TDR motion in patients without ASD was 4.7 degrees versus 1.6 degrees in patients with ASD (p<0.035). Statistical analysis with the small numbers available failed to show a significant correlation between radiographic ASD and clinical outcome.[2]

Deeper investigation into radiographic ASD after TDR showed that in this cohort of patients, those with TDR ROM greater than or equal to 5 degrees had a 0% prevalence of ASD at 8.7 years [3], well below the rate of ASD seen after fusion. These data suggest that motion preservation has the ability to reduce the incidence of ASD. While we are disappointed in the relatively low ROM achieved by this first-generation Prodisc implant, the fact that maintenance of ROM seems to prevent ASD points to the need for further optimization of implant designs to maximize motion.

Difficulty implanting the SB Charite device in multilevel cases was not directly observed in this study of the first-generation Prodisc implant, but was reported separately by Cinnotti et al.[4]

Sincerely,

Patrick Tropiano, Russel C.Huang, Federico P Girardi, Frank P. Cammisa, Jr., Thierry Marnay

References:

1. Huang RC, Girardi FP, Cammisa Jr FP, Tropiano P, Marnay T. Long- term flexion-extension range of motion of the prodisc total disc replacement. J Spinal Disord Tech 2003;16:435-40.

2. Huang RC, Girardi FP, Cammisa Jr FP, Lim MR, Tropiano P, Marnay T. The relationship between range of motion and outcome in lumbar total disc replacement at 9-year follow-up. North American Spine Society 19th Annual Meeting. Chicago, IL, 2004.

3. Huang RC, Girardi FP, Lim MR, Cammisa Jr FP, Tropiano P, Marnay T. Range of motion and adjacent level degeneration after lumbar total disc replacement. Scoliosis Research Society 39th Annual Meeting. Buenos Aires, Argentina, 2004.

4. Cinotti G, David T, Postacchini F. Results of disc prosthesis after a minimum follow-up period of 2 years. Spine 1996;21:995-1000.
Lumbar Total Disc Replacement 20 April 2005
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Bipin Theruvil, FRCS,
Specialist Registrar
St Mary's Hospital, Isle of Wight, UK,
Praveen Mundlur, Chris Dare, Elias Rahall

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Re: Lumbar Total Disc Replacement

bipintheruvil{at}aol.com Bipin Theruvil, FRCS, et al.

To the Editor:

We read the article “Lumbar Total Disc Replacement. Seven to Eleven-Year Follow-up” (1) with great interest and congratulate Marnay, et al, on their excellent study. We are quite reassured to find that there was no incidence of polyethylene wear in any of their cases.

The authors mention that one of the main advantages of disc arthroplasty, as compared to fusion, is the ability to prevent adjacent segment degeneration (ASD). Preservation of segmental motion is essential to prevent ASD. We would be very interested to know if the range of movement of the replaced discs was maintained in the long term in the 64 patients and if so how was this evaluated. We would be keen to know if the authors observed any ASD in their group of patients.

This study incidentally has the longest follow up (8.7years) among the articles on disc arthoplasty reported so far. In another recent article, 27.4% patients developed ASD and underwent decompression or arthrodesis, at an average follow up of 6.7 years following lumbar spine fusion (2).

In our hospital, the SB Charité Disc is our implant of choice. We have experience with this prosthesis in 39 patients of which 9 cases were 2 level disc replacements. In contrast to the opinion of the authors we have not encountered problems in obtaining distraction at the second level with this particular prosthesis.

Yours sincerely,

P. Mundlur

B. Theruvil

C. Dare

E. Rahall

Reference:

(1)Patrick Tropiano, Russel C. Huang, Federico P. Girardi, Frank P. Cammisa, Jr., and Thierry Marnay Lumbar Total Disc Replacement. Seven to Eleven-Year Follow-Up J Bone Joint Surg Am 2005; 87: 490-496

(2) Ghiselli G, Wang JC, Bhatia NN, Hsu WK, Dawson EG, Adjacent segment degeneration in the lumbar spine.J Bone Joint Surg Am. 2004 Jul;86 -A(7):1497-503.